Interpenetrating polymer networks using blocked polyurethane/polyurea prepolymers for golf ball layers

ABSTRACT

The present invention is directed to a method of forming a golf ball that contains an interpenetrating polymer network, or IPN, which includes at least two polymeric systems, in one or more of the layers. The first polymeric system may include a polyurethane-based or polyurea-based system having blocked isocyanate groups and the second polymeric system may include an epoxy-based or acrylic-based system, wherein the two systems are polymerized or cured simultaneously or sequentially to form an IPN.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation-in-part of U.S. patent application Ser.No. 09/833,667, filed on Apr. 13, 2001, now pending, which isincorporated by reference herein in its entirety.

FIELD OF THE INVENTION

[0002] The present invention is directed to a golf ball that contains aninterpenetrating polymer network, or “IPN,” formed from at least twochemically different polymeric components intertwined with each other.The IPN includes a blocked polymeric component and its respective curingagent, catalyst, and/or initiator. The method of forming a golf ballcontaining an IPN of the invention in one or more of golf ball layers isalso an aspect of the present invention.

BACKGROUND OF THE INVENTION

[0003] Golf balls are formed from a variety of compositions. Forexample, golf ball covers may be formed from balata, a natural orsynthetic trans-polyisoprene rubber, ionomer resins, a durablethermoplastic material, or polyurethanes or polyureas, relatively softthermoset or thermoplastic materials. Balata covered balls are favoredby more highly skilled golfers because the softness of the cover allowsthe player to achieve spin rates sufficient to more precisely controlball direction and distance, particularly on shorter shots. However,balata covered balls are easily damaged, and thus lack the durabilityrequired by the average golfer.

[0004] Ionomer resins have more or less replaced balata as a covermaterial. Chemically, ionomer resins are a copolymer of an olefin and anα, β-ethylenically-unsaturated carboxylic acid having at least a portionof the acid groups neutralized by a metal ion, as disclosed in U.S. Pat.No. 3,264,272. Commercially available ionomer resins include, but arenot limited to, SURLYN® from DuPont de Nemours and Company, and ESCOR®and IOTEK® from Exxon Corporation. These ionomer resins aredistinguished by the type of metal ion, the amount of acid, and thedegree of neutralization. While these ionomers provide extremely durablecovers, however, the spin and feel are inferior compared to balatacovered balls.

[0005] Polyurethanes have also been recognized as useful materials forgolf ball covers since about 1960. Polyurethanes are the reactionproduct of a polyisocyanate and a polyol cured with a hydroxy-terminatedor amine-terminated curing agent. U.S. Pat. Nos. 3,147,324, 4,123,061,and 5,334,673 are directed to methods of making golf balls having apolyurethane cover. The resulting golf balls are durable, while at thesame time maintaining the softer “feel” of a balata ball. However, golfball covers made from polyurethane have not, to date, fully matchedSURLYN® golf balls with respect to resilience or the rebound of the golfball cover, which is a function of the initial velocity of a golf ballafter impact with a golf club.

[0006] Polyureas have also been proposed as cover materials for golfballs. For instance, U.S. Pat. No. 5,484,870 discloses a polyureacomposition formed from the reaction product of an organic isocyanateand an organic amine, each having at least two functional groups. Oncethese two ingredients are combined, the polyurea is formed, and thus theability to vary the physical properties of the composition is limited.Like polyurethanes, conventional polyureas are not completely comparableto SURLYN® golf balls with respect to resilience or the rebound ordamping behavior of the golf ball cover.

[0007] In addition, epoxy resins and acrylate resins have been used ingolf ball compositions as compatibilizers. For example, WO 92/12206discloses a resin composition for golf balls formed from a polyesterblock copolymer and an ionomer resin, and also including anepoxy-containing compound to improve compatibility between the twopolymers. The resultant compositions are purported to have improveddelamination resistance, flexibility and modulus of resilience, however,the inclusion of such epoxy-containing copolymers increases the meltviscosity of the resin compositions, which makes the compositionsunusuable for certain molding applications. In addition, U.S. Pat. No.5,321,089 describes a compatibilizers that contains a small amount ofacrylate resins to be used in an ionomer-based golf ball covercomposition. The disclosed balls had durability properties superior tobalata-covered balls, but inferior to golf balls having covers formedfrom ionomer blends.

[0008] As shown above, the majority of conventional compositions forgolf balls have advantages and drawbacks when used in a golf ball layer.As such, golf ball manufacturers are continually searching forcompositions that deliver an ideal balance for golfers of all skilllevels without sacrificing performance benefits, manufacturingefficiencies, or feel.

[0009] Interpenetrating polymer networks, or IPNs, are occasionally usedto improve key physical properties or to aid in the compatibilization ofthe components of a polymer mixture or blend. For example, the use ofIPNs may assist in improving durability, e.g., improving fracturetoughness and microcracking resistance, and thermal and mechanicalperformance. Various IPNs are discussed in U.S. Pat. Nos. 5,648,432,5,210,109, and 4,923,934. For example, U.S. Pat. Nos. 4,128,600,4,247,578, and 4,342,793 disclose IPN technology for plastics based on atwo-component urethane system polymerized simultaneously with an acrylicmonomer. In addition, U.S. Pat. No. 4,923,934 discloses the formation ofan IPN from the reaction of a blocked urethane prepolymer, a polyol, andepoxy resin, and an epoxy-catalyzing agent, such as an anhydride for usein coating applications.

[0010] Therefore, it would be advantageous to use the IPN concept toform a composition that capitalizes on the favorable properties, butcompensates for deficiencies, of individual polymeric systems typicallyused for golf ball components. In particular, it would be beneficial touse an IPN that utilizes several polymeric components, compatibilizers,and blocking agents in order to achieve a golf ball composition thatmaximizes beneficial properties and minimizes potential problems. Thepresent invention provides such compositions.

SUMMARY OF THE INVENTION

[0011] The present invention relates to an interpenetrating polymernetwork in a golf ball. In particular, the present invention relates toa method of forming a portion of a golf ball comprising the steps ofproviding at least a first polymeric component and a second polymericcomponent, each polymeric component comprising at least one monomer,oligomer, prepolymer, or a combination thereof; sufficientlypolymerizing each polymeric component sequentially or simultaneously toform a polymer or polymer network; crosslinking each polymer or polymernetwork to the other polymer or polymer network to form aninterpenetrating polymer network (“IPN”); and forming the IPN into theportion of the golf ball, wherein each polymeric component of themixture is polymerized by exposing the mixture to at least one energysource, at least one initiator, or a combination thereof for a timesufficient to polymerize said polymeric component.

[0012] In another embodiment, the at least one energy source is selectedfrom the group consisting of microwave radiation, infrared radiation,visible radiation, ultraviolet radiation, x-ray radiation, gammaradiation, electron beam radiation and a combination thereof. In anotherembodiment, the at least one initiator is selected from the groupconsisting of a thermal free radical initiator, a photoinitiator, acationic initiator, and a mixture thereof.

[0013] In a preferred embodiment, the thermal free radical initiator isselected from the group consisting of an azo compound, a peroxide, apersulfate, a redox initiator, and mixtures thereof. In anotherpreferred embodiment, the photoinitiator is selected from the groupconsisting of a peroxide, an azo compound, quinine, benzophenone,nitroso compound, acyl halide, hydrazone, a mercapto compound, apyrylium compound, a triacylimidazole, an organophosphorus compounds, abisimidazole, a chloroalkyltriazine, a benzoate, a benzoyl compound, abenzoin ether, a benzil ketal, a thioxanthone, an acetophenonederivative, a ketone, a metallocene, a hexafluorophosphate salt, asulfonium salt, a diacrylate, a polyol, a pyrollidone, and mixturesthereof. In yet another preferred embodiment, the cationic initiator isselected from the group consisting of a Group IA organo compound, GroupIIA organo compound, aryl sulfonium salt, hexafluorometallic salt,Bronsted acid, Lewis acid, and mixtures thereof. Typically, theinitiator is present in an amount of greater than about 0.1 parts perhundred of total polymer component. Preferably, the initiator is presentin an amount from about 0.1 to about 15 parts per hundred of totalpolymer component.

[0014] In one embodiment, the polymerization of each polymeric componentis subsequent or simultaneous with the crosslinking of each polymer orpolymer network to the other polymer or polymer network. In anotherembodiment, the first polymeric component is polymerized in the presenceor absence of at least a second polymeric component to form a firstpolymer or first polymer network. In yet another embodiment, the secondpolymeric component is polymerized in the presence of the firstpolymeric component or the first polymer or first polymer network toform a second polymer or second polymer network. In another embodiment,crosslinking of the first polymer or first polymer network to the secondpolymer or second polymer network occurs subsequently or simultaneouslywith the polymerization of the second polymeric component to form thesecond polymer or second polymer network. In yet another embodiment, thepolymerization of each polymeric component and the crosslinking of eachpolymer or polymer network to the other polymer or polymer networkoccurs simultaneously to form an IPN.

[0015] In one embodiment, the first polymeric component and the secondpolymeric component include monomeric, oligomeric or prepolymericprecursors of vinyl resins; polyolefins; polyurethanes; polyureas;polyamides; polyamide/polyurethane copolymers, polyamide/polyureacopolymers, epoxy-end-capped polyurethanes, epoxy-end-capped polyureas,polyamide/polyurethane ionomers, polyamide/polyurea ionomers, acrylicresins; olefinic rubbers; polyphenylene oxide resins; polyesters; blendsof vulcanized, unvulcanized or non-vulcanizable rubbers withpolyethylene, polypropylene, polyacetal, nylon, polyesters, or celluloseesters; or polymers or copolymers possessing epoxy-containing, orpost-polymerization epoxy-functionalized repeat units.

[0016] In a preferred embodiment, the method further comprises providinga golf ball center; and disposing the IPN about the center to provide aportion of the golf ball. In another embodiment, the IPN is included inan intermediate layer disposed about the center. In another embodiment,the IPN is included in a cover layer disposed about the center.

[0017] The present invention is also directed to a method of forming aportion of a golf ball comprising the steps of providing a firstpolymeric component comprising at least one monomer, oligomer,prepolymer, or a combination thereof; sufficiently polymerizing thefirst polymer component to form a first polymer or first polymernetwork; providing a second polymeric component comprising at least onemonomer, oligomer, prepolymer, or a combination thereof; sufficientlypolymerizing the second polymer component to form a second polymer orsecond polymer; and crosslinking the first polymer or first polymernetwork with the second polymer or second polymer network to form anIPN.

[0018] In one embodiment, the first polymeric component is polymerizedby exposing the first polymeric component to a first energy source, afirst initiator, or a combination thereof for a time sufficient topolymerize the first polymeric component. In a preferred embodiment, thefirst energy source is selected from the group consisting of microwaveradiation, infrared radiation, visible radiation, ultraviolet radiation,x-ray radiation, gamma radiation, electron beam radiation and acombination thereof. In another preferred embodiment, the firstinitiator is selected from the group consisting of a thermal freeradical initiator, a photoinitiator, a cationic initiator, and a mixturethereof. In one embodiment, the first initiator is present in an amountof greater than about 0.01 parts per hundred of the first polymericcomponent. In a preferred embodiment, the initiator is present in anamount from about 0.01 to about 15 parts per hundred of total polymercomponent.

[0019] In another embodiment, the second polymeric component ispolymerized by exposing the second polymeric component to a secondenergy source, a second initiator, or a combination thereof for a timesufficient to polymerize the second polymeric component. In a preferredembodiment, the second energy source is selected from the groupconsisting of microwave radiation, infrared radiation, visibleradiation, ultraviolet radiation, x-ray radiation, gamma radiation,electron beam radiation and a combination thereof. In a more preferredembodiment, the second energy source is electron beam radiation.

[0020] In another preferred embodiment, the second initiator is selectedfrom the group consisting of a thermal free radical initiator, aphotoinitiator, a cationic initiator, and a mixture thereof. In oneembodiment, the second initiator is present in an amount of greater thanabout 0.01 parts per hundred of the first polymeric component. In apreferred embodiment, the initiator is present in an amount from about0.01 to about 15 parts per hundred of total polymer component.

[0021] In one embodiment, the first polymeric component is polymerizedin the presence or absence of at least a second polymeric component toform a first polymer or first polymer network. In another embodiment,the second polymeric component is polymerized in the presence of thefirst polymeric component or the first polymer or first polymer networkto form a second polymer or second polymer network. In yet anotherembodiment, crosslinking of the first polymer or first polymer networkto the second polymer or second polymer network occurs subsequently orsimultaneously with the polymerization of the second polymeric componentto form the second polymer or second polymer network.

[0022] In one embodiment, the first polymeric component and the secondpolymeric component comprise monomeric, oligomeric or prepolymericprecursors of vinyl resins; polyolefins; polyurethanes; polyureas;polyamides; acrylic resins; olefinic rubbers; polyphenylene oxideresins; polyesters; blends of vulcanized, unvulcanized ornon-vulcanizable rubbers with polyethylene, polypropylene, polyacetal,nylon, polyesters, or cellulose esters; or polymers or copolymerspossessing epoxy-containing, or post-polymerization epoxy-functionalizedrepeat units.

[0023] In one embodiment, the portion of the golf ball formed from theIPN is a core, intermediate layer or cover layer. In a preferredembodiment, the method further comprises providing a golf ball center;and disposing the IPN about the center to provide a portion of the golfball. In a more preferred embodiment, the IPN is included in anintermediate layer disposed about the center. In another more preferredembodiment, the IPN is included in a cover layer disposed about thecenter.

[0024] The present invention is also directed to a golf ball includingat least one layer, e.g., the cover layer, formed from aninterpenetrating polymer network including a first polymeric systemincluding a polyurethane or polyurea prepolymer cured with a firstcuring agent, wherein the prepolymer includes an isocyanate havingterminal isocyanate groups, a blocking agent, and a polyol or apolyamine; and a second polymeric system including a) an epoxy resin anda second curing agent or b) an acrylate resin and an initiator. At leastabout 80 percent of the terminal isocyanate radicals groups arepreferably blocked. For instance, at least about 95 percent or more ofthe terminal isocyanate groups may be blocked. In one embodiment, atleast about 97 percent or more of the terminal isocyanate groups areblocked.

[0025] In this aspect of the invention, the blocking agent is selectedfrom the group consisting of linear and branched alcohols; phenols andphenol derivatives; oximes; lactams; lactones; β-dicarbonyl compounds;hydroxamic acid esters; bisulfite addition compounds; hydroxylamines;esters of p-hydroxybenzoic acid; N-hydroxyphthalimide;N-hydroxysuccinimide; triazoles; substituted imidazolines;tetrahydropyrimidines; caprolactones; and mixtures thereof. For example,the blocking agent may be selected from the group consisting of phenols,branched alcohols, methyl ethyl ketoxime, ε-caprolactam, ε-caprolactone,and mixtures thereof.

[0026] In another embodiment, the second curing agent is selected fromthe group consisting of anhydrides, Lewis bases, amines, amides, Lewisacids, and mixtures thereof. The initiator may include benzoyl peroxide,t-amyl peroxide, or mixtures thereof.

[0027] The cover layer may include an inner cover layer and an outercover layer, and wherein the outer cover layer includes theinterpenetrating polymer network.

[0028] The present invention is also directed to a golf ball including acore and a cover, wherein a portion of the golf ball is formed from aninterpenetrating polymer network including a first polymeric systemincluding an isocyanate having terminal isocyanate groups, a polyol oramine-terminated component, and a blocked, delayed action curative; anda second polymeric system including a) an acrylate resin and aninitiator or b) an epoxy resin and a curing agent. In one embodiment,the blocked delayed action curative includes methylene dianiline andsodium chloride having a deblocking temperature of about 175° F. toabout 350° F.

[0029] In another embodiment, the first polymeric system is saturated.In another embodiment, the first polymeric system further includes acatalyst including an organometallic compound, tertiary amine, orcombination thereof. When the second polymeric system is formedincluding an acrylate resin and an initiator, the initiator may includebenzoyl peroxide, t-amyl peroxide, or mixtures thereof. And, when thesecond polymeric system includes an epoxy resin and a curing agent, thecuring agent may be selected from the group consisting of anhydrides,Lewis bases, amines, amides, Lewis acids, and mixtures thereof.

[0030] In this aspect of the invention at least about 80 percent of theterminal isocyanate radicals groups are preferably blocked. Forinstance, at least about 95 percent or more, about 97 percent or more,or substantially all, of the terminal isocyanate groups may be blocked.

[0031] The golf ball may be of any construction. For example, in oneembodiment, the golf ball includes an intermediate layer, which may beformed of a thermoplastic material. In another embodiment, the portionincluding the interpenetrating polymer network includes the cover.

[0032] The present invention is further directed to a method of forminga portion of a golf ball including the steps of:

[0033] providing a first polymeric component including a polyurethane orpolyurea prepolymer having blocked isocyanate groups;

[0034] providing a second polymeric component including a) an epoxyresin or b) an acrylate resin;

[0035] sufficiently polymerizing the first and second polymericcomponents sequentially or simultaneously to form first and secondpolymeric systems;

[0036] crosslinking each polymeric system to the other polymeric systemto form an interpenetrating polymer network (“IPN”); and

[0037] forming the IPN into the portion of the golf ball,

[0038] wherein each polymeric component of the mixture is polymerized byexposing the mixture to an energy source, curing agent, or a combinationthereof for a time sufficient to polymerize the polymeric component.

[0039] In one embodiment, at least about 80 percent, preferably about 90percent, of the isocyanate groups are blocked. In another embodiment,the step of forming the first polymeric component further includes thesteps of: providing an isocyanate having terminal isocyanate groups;providing a polyol or amine-terminated component; reacting theisocyanate and polyol or amine-terminated component to form aprepolymer; and blocking the terminal isocyanate groups. In yet anotherembodiment, the step of blocking the terminal isocyanate groups furtherincludes the steps of: providing a blocking agent; and blocking theterminal isocyanate groups with the blocking agent to form a blockedprepolymer.

[0040] In still another embodiment, the step of forming the firstpolymeric component further includes the steps of: providing anisocyanate having terminal isocyanate groups; providing a blockingagent; reacting the isocyanate and blocking agent to form a half-blockedintermediate; providing a polyol or amine-terminated component; reactingthe half-blocked intermediate with a polyol or amine-terminatedcomponent to form a prepolymer.

[0041] The step of sufficiently polymerizing the first and secondpolymeric components may further include providing a first curing agentfor the first polymeric component and a second curing agent for thesecond polymeric component. When the second polymeric system is anacrylate resin and an initiator, the step of sufficiently polymerizingthe first and second polymeric components may further include providinga first curing agent for the first polymeric component and an initiatorfor the second polymeric component.

[0042] The blocking agent may include linear and branched alcohols;phenols and phenol derivatives; oximes; lactams; lactones; β-dicarbonylcompounds; hydroxamic acid esters; bisulfite addition compounds;hydroxylamines; esters of p-hydroxybenzoic acid; N-hydroxyphthalimide;N-hydroxysuccinimide; triazoles; substituted imidazolines;tetrahydropyrimidines; caprolactones; or mixtures thereof.

[0043] In this aspect of the invention, the at least one energy sourceis selected from the group consisting of microwave radiation, infraredradiation, visible radiation, ultraviolet radiation, x-ray radiation,gamma radiation, electron beam radiation and a combination thereof.

[0044] In one embodiment, the polymerization of each polymeric componentis subsequent or simultaneous with the crosslinking of each polymericsystem to the other polymeric system. In another embodiment, thepolymerization of each polymeric component and the crosslinking of eachpolymeric system to the other polymeric system occurs simultaneously toform an IPN. In still another embodiment, the IPN included in a coverlayer disposed about a center.

[0045] The present invention is also directed to a method of forming aportion of a golf ball including the steps of:

[0046] providing a first polymeric component including an isocyanate, apolyol or amine-terminated component, and a blocked, delayed actioncurative;

[0047] providing a second polymeric component including an epoxy resinor acrylate resin;

[0048] sufficiently polymerizing the first and second polymericcomponents sequentially or simultaneously to form first and secondpolymeric systems;

[0049] crosslinking each polymeric system to the other polymeric systemto form an interpenetrating polymer network (“IPN”); and

[0050] forming the IPN into the portion of the golf ball,

[0051] wherein each polymeric component of the mixture is polymerized byexposing the mixture to an energy source, curing agent, or a combinationthereof for a time sufficient to polymerize the polymeric component.

[0052] In one embodiment, the step of sufficiently polymerizing thefirst and second polymeric components further includes the steps of:elevating the temperature to deblock the blocked, delayed actioncurative; and providing a curing agent or initiator for the secondpolymeric component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Further features and advantages of the invention can beascertained from the following detailed description that is provided inconnection with the drawings described below:

[0054]FIG. 1 illustrates a golf ball including a center and a coverlayer disposed over the center, in which at least one of the center orthe cover layer includes an IPN.

[0055]FIG. 2 illustrates a multi-layer golf ball including a center, anintermediate layer disposed over the center, and a cover layer disposedover the intermediate layer, in which at least one part of the golf ballincludes an IPN.

[0056]FIG. 3 illustrates a multi-layer golf ball including a core, anintermediate layer, and a cover layer disposed over the core, in whichat least one part of the golf ball includes an IPN.

DETAILED DESCRIPTION OF THE INVENTION

[0057] The present invention relates to compositions includinginterpenetrating polymer networks. (IPNs) formed from two differentpolymer chains. The IPNs may be formed using a blocked polyurethaneprepolymer and an epoxy resin. In addition, an IPN of the presentinvention may be formed using a blocked polyurea prepolymer and anacrylate functional resin. Each system includes a curing agent for theprepolymer and a curing agent/catalyzing agent/initiator for the secondpolymeric component, i.e., the epoxy resin or acrylate functional resin.

[0058] The compositions of the invention may be used with golf balls ofvarious constructions, e.g., one-piece golf balls, two-piece golf balls,or multilayer golf balls having a center, at least one intermediatelayer disposed concentrically adjacent to the center, and at least onecover layer.

[0059] The Compositions of the Invention

[0060] As briefly discussed above, the compositions of the inventioninclude an IPN, which generally improve the compatibility of polymericcomponents. IPNs are formed when polymerizable compositions areindependently reacted to form distinct, intertwining, continuouspolymeric chains. Combining chemically different types of polymericnetworks results in the formation of resins having different properties.The interpenetrating polymer network produced exhibits properties thatare different from the individual constituent polymers. In accordance,the term “interpenetrating polymer network” or “IPN”, as used herein,refers to two chemically different polymer chains intertwined with eachother.

[0061] IPNs useful for the present invention may include two or moredifferent polymers or polymer networks and can encompass any one or moreof the different types of IPNs listed and described below, which mayoverlap:

[0062] (1) Sequential IPNs, in which monomers or prepolymers forsynthesizing one polymer or a polymer network are polymerized in thepresence of another polymer or polymer network. These networks may havebeen synthesized in the presence of monomers or prepolymers of the onepolymer or polymer network, which may have been interspersed with theother polymer or polymer network after its formation or cross-linking;

[0063] (2) Simultaneous IPNs, in which monomers or prepolymers of two ormore polymers or polymer networks are mixed together and polymerizedand/or crosslinked simultaneously, such that the reactions of the twopolymer networks do not substantially interfere with each other;

[0064] (3) Grafted IPNs, in which the two or more polymers or polymernetworks are formed such that elements of the one polymer or polymernetwork are occasionally attached or covalently or ionically bonded toelements of an/the other polymer(s) or polymer network(s);

[0065] (4) Semi-IPNs, in which one polymer is cross-linked to form anetwork while another polymer is not; the polymerization or crosslinkingreactions of the one polymer may occur in the presence of one or moresets of other monomers, prepolymers, or polymers, or the composition maybe formed by introducing the one or more sets of other monomers,prepolymers, or polymers to the one polymer or polymer network, forexample, by simple mixing, by solublizing the mixture, e.g., in thepresence of a removable solvent, or by swelling the other in the one;

[0066] (5) Full, or “true,” IPNs, in which two or more polymers or setsof prepolymers or monomers are crosslinked (and thus polymerized) toform two or more interpenetrating crosslinked networks made, forexample, either simultaneously or sequentially, such that the reactionsof the two polymer networks do not substantially interfere with eachother;

[0067] (6) Homo-IPNs, in which one set of prepolymers or polymers can befurther polymerized, if necessary, and simultaneously or subsequentlycrosslinked with two or more different, independent crosslinking agents,which do not react with each other, in order to form two or moreinterpenetrating polymer networks;

[0068] (7) Gradient IPNs, in which either some aspect of thecomposition, frequently the functionality, the copolymer content, or thecrosslink density of one or more other polymer networks gradually varyfrom location to location within some, or each, other interpenetratingpolymer network(s), especially on a macroscopic level;

[0069] (8) Thermoplastic IPNs, in which the crosslinks in at least oneof the polymer systems involve physical crosslinks, e.g., such as verystrong hydrogen-bonding or the presence of crystalline or glassy regionsor phases within the network or system, instead of chemical or covalentbonds or crosslinks; and

[0070] (9) Latex IPNs, in which at least one polymer or set ofprepolymers or monomers are in the form of lattices, frequently (thoughnot exclusively) in a core-shell type of morphology, which form aninterpenetrating polymer network when dried, for example, as a coatingon a substrate (if multiple polymers or sets of prepolymers or monomersare in the form of lattices, this is sometimes called an“interpenetrating elastomer network,” or IEN).

[0071] The polymer chains may be crosslinked, however, no apparentchemical bonding should occur between the polymer chains, i.e.,inter-crosslinking, with the exception of the occasional/accidentalcovalent bond. Thus, it should be understood that an IPN according tothe invention should not include a copolymer network. The term“copolymer network,” as used herein, can be defined as a single polymernetwork formed from two or more different types of monomers, oligomers,precursor packages, or polymers, during which network formation: a) thecrosslinking reaction(s) result(s) in the different types of polymers,oligomers, or precursors being sufficiently inter-crosslinked, i.e., thepolymers, oligomers, or precursors of one or more types are connected topolymers, oligomers, or precursors of the other different types, suchthat effectively one crosslinked network connecting all the differentmonomers, oligomers, precursors, or polymers is formed; b) thecontemporaneous or consecutive polymerization reaction(s) of all thedifferent types of monomers, oligomers, or precursors result(s) in twoor more different types of copolymers, which may themselves beoligomeric or polymeric and may be precursors to (an)other type(s) ofcopolymer(s), and which may then undergo inter-crosslinking reaction(s),as in a), between the different types of copolymers; c) thecontemporaneous or consecutive polymerization reaction(s) of all thedifferent types of monomers, oligomers, or precursors result(s) in asingle type of copolymer, which may itself be oligomeric or polymericand may be a precursor to another type of copolymer, and which may thenundergo a sufficient intra-crosslinking reaction, i.e., the copolymerchains of the single type are connected to other copolymer chains of thesame type, such that effectively a single crosslinked network connectingcopolymer chains is formed; or d) any combination thereof.

[0072] For example, a grafted IPN is distinguishable from a copolymernetwork, in that the inter-crosslinking of a grafted IPN is onlyoccasional, resulting in relatively few cross-type polymer linkages,while the inter-crosslinking of a copolymer network occurs relativelyfrequently, resulting in a relatively large amount of cross-type polymerlinkages. As a result, the copolymer network is effectively a singlecopolymer network, while the grafted IPN according to the invention maybe lightly inter-crosslinked but is effectively a combination of atleast two, preferably co-continuous, polymer networks. Preferably,grafted IPNs according to the invention have a substantial lack ofcross-type polymer linkages, or inter-crosslinking. In the context ofthe present invention, a component that has a “substantial lack of” anitem should be understood to have less than about 20 percent, preferablyto have less than about 10 percent, more preferably to be substantiallyfree of that item. As used herein, the phrase “substantially free of”means that there is less than about 5 percent, preferably less thanabout 2 percent, and more preferably less than about 1 percent of thatitem present. Most preferably, it means that the component orcomposition is completely free of that item. In one embodiment, a layercontaining a gradient IPN according to the invention has a flexuralmodulus below about 5 ksi.

[0073] With the exception of grafted IPNs above, all forms ofcrosslinking recited in the descriptions of IPNs above should hereby beunderstood to be intra-crosslinks, or same-type polymer linkages, i.e.,crosslinks between polymer chains made from the same precursor package.Still, grafted IPNs predominantly contain intra-crosslinks, but alsocontain a small amount of inter-crosslinks.

[0074] It should also be understood that an IPN according to theinvention should not include a combination of an individual polymer anda polymer network of essentially the same type as the individualpolymer, e.g., a single type of homopolymer or copolymer, such as PMMA,that has been: a) incompletely crosslinked, such as by incorporation ofan appropriate amount of diacrylate monomer; or b) incompletely orcompletely crosslinked and then blended with uncrosslinked, neat PMMA,is not considered an IPN according to the present invention, despite itspossible characterization as a semi-homo-IPN. Such a combination isconsidered a partially-crosslinked, single-polymer network or system.

[0075] IPNs of the present invention contain two or more polymers, atleast one of which is crosslinked to form a network. In consideringpolymers useful in golf balls of the present invention, examples includecrosslinked or uncrosslinked incarnations of any polymer capable ofbeing incorporated into an interpenetrating polymer network.Particularly exemplary polymers include, but are not limited to,polyurea, polyamide/polyurethane copolymer, polyamide/polyureacopolymer, epoxy-end-capped polyurethane, epoxy-end-capped polyurea,polyamide/polyurethane ionomers, polyamide/polyurea ionomers, urethanepolymers or copolymers, polymers made from an epoxy-containingprecursor, polymers having backbone or pendant ester groups, polyimidesor copolymers containing imide groups, polymers or copolymers containingsiloxane groups, polymers or copolymers containing silane groups,acrylate polymers or copolymers (including, but not limited to, mono-,di-, tri, and/or tetra-acrylates), alkyl acrylate polymers orcopolymers, alkyl alkyl-acrylate polymers or copolymers, for example,such as poly(methyl methacrylate) and the like, polyacrylic acids orpoly(alkyl-acrylic acids), including, but not limited to, monomers suchas acrylic acid or methacrylic acid, polymers or copolymers containingvinyl acetate repeat units, polymers or copolymers containing halogengroups, polymers or copolymers containing a uretdione group, polymers orcopolymers containing an oxazolidone group, or mixtures thereof. Otherexamples of useful polymers may include polymers or copolymerscontaining or made from a conjugated diene, polymers or copolymerscontaining a styrenic moiety, ionomeric polymers or copolymers, ormixtures thereof. Preferred first, second or more polymeric componentsinclude monomeric, oligomeric or prepolymeric precursors of vinylresins, polyolefins, polyurethanes, polyureas, polyamide and mixturesand copolymers thereof, such as those described in U.S. Pat. Nos.6,646,061, 6,645,091, 6,648,776, and copending U.S. patent applicationSer. No. 10/190,705, the entirety of which are incorporated herein.

[0076] In one embodiment, the IPN of the present invention includes afirst polymeric system including a blocked prepolymer and a secondpolymeric system including an epoxy resin or acrylate resin. The blockedprepolymer may be polyurea-based or polyurethane-based. The specifics ofthe polymeric system are discussed in more detail below.

[0077] When the second polymeric component is an epoxy resin, theblocked prepolymer is mixed with the second polymeric component in thepresence of a curing agent/catalyzing agent and a short chainamine-terminated component or a short chain hydroxy-terminatedcomponent. For example, once the mixed material is heated to thetemperature necessary for deblocking the isocyanate groups, theprepolymer reacts with the short chain amine-terminated component orshort chain hydroxy-terminated component to form a cured polyurea-basedsystem or polyurethane-based system. At the same time, the epoxy systemreacts with the curing agent/catalyzing agent to form a cured epoxysystem. The two cured systems form an IPN.

[0078] In the alternative, a “deblocking” agent may be added to themixed material to react with the blocked isocyanate groups, which allowsthe prepolymer to react with the curing agent to form a curedpolyurea-based system or polyurethane-based system. The epoxy systemsimultaneously or sequentially reacts with its respective curingagent/catalyzing agent to form a cured epoxy system. The two curedsystems form an IPN according to the present invention.

[0079] Likewise, when the second polymeric component is an acrylicresin, the blocked prepolymer is mixed with the second polymericcomponent in the presence of an initiator to cure the second polymericcomponent and a short chain amine-terminated component or a short chainhydroxy-terminated component to cure the prepolymer.

[0080] In the alternative, an excess of the short chain amine-terminatedor hydroxy-terminated component may be included in an amount sufficientto cure both the first and second polymeric components (instead of usinga separate curing agent/catalyzing component for the second polymericcomponent) for either type of IPN, i.e., an IPN including an epoxysystem or an IPN including an acrylic resin system.

[0081] It is important to note that when a short chainhydroxy-terminated component is used as a curing agent for apolyurea-based prepolymer, the resulting polyurea-based system willcontain urethane linkages as a result of the excess isocyanate reactingwith the hydroxy groups of the curing agent. Thus, for the purposes ofthe present invention, such a system is referred to as apolyurea-urethane system as opposed to a polyurea system, which containsonly urea linkages. Likewise, a polyurethane prepolymer cured with anamine-terminated curing agent will produce a system including bothurethane and urea linkages and will thus be referred to as apolyurethane-urea system. Examples of suitable curing agents/catalyzingagents for the epoxy resin, initiators for the acrylic resins, andamine-terminated and hydroxy-terminated curing agents for the prepolymerwill be discussed in greater detail below.

[0082] The First Polymeric System

[0083] A blocked urethane or urea prepolymer may form the firstpolymeric system of an IPN of the present invention. In particular, theurethane or urea can be blocked to prevent premature polymerization orcrosslinking of the polyisocyanate groups. Because the two polymericsystems of the IPN may be cured simultaneously, the isocyanates groupsmay be subjected to heat to deblock the isocyanates once the prepolymercuring agent and curing agent/catalyzing agent/initiator are added tocure the two polymeric systems and form the IPN. In the alternative, a“deblocking” agent may be used to react with the blocked isocyanategroups in order to allow the isocyanate groups to react with the curingagent to form the first polymeric system.

[0084] In the context of the present invention, the term “prepolymer”refers generally to a macromonomer or partially polymerized materialformed by the reaction product of at least two components, each having afunctionality that is reactive with at least one other component underthe appropriate circumstances, which macromonomer or partiallypolymerized material can be subsequently reacted with at least one othercomponent (which may be the same as one of the at least two componentsor different) to form a polymer. In particular, a “prepolymer” may referto a material containing at least one isocyanate-containing componentand at least one isocyanate-reactive component, for example, such as apolyol, a polyamine, an epoxy-containing compound, or a mixture thereof.Alternatively, “prepolymers” according to the present invention may notinclude an isocyanate-containing component.

[0085] As briefly mentioned above, the prepolymer used in this aspect ofthe invention may be a polyurethane prepolymer or a polyurea prepolymer.The polyurea prepolymer is the reaction product of an amine-terminatedcomponent and an isocyanate, whereas the polyurethane prepolymer is thereaction product of a hydroxy-terminated component and an isocyanate.The particular components of the prepolymers will be discussed ingreater detail below.

[0086] Because the main difference between the polyurea prepolymer andthe polyurethane prepolymer is the amine-terminated component/polyolcomponent, the isocyanates discussed are intended to be used in eithertype of prepolymer.

[0087] The Isocyanate Component

[0088] Any isocyanate having two or more isocyanates groups, e.g., twoto four isocyanate groups, bonded to an organic radical, may be used inthe prepolymers of the present invention. The general formula of asuitable isocyanate for use with the present invention is as follows:

R—(NCO)_(x)

[0089] where R may be any organic radical having a valence x. In oneembodiment, R is a straight or branched hydrocarbon moiety, acyclicgroup, cyclic group, heterocyclic group, aromatic group, phenyl group,hydrocarbylene group, or a mixture thereof. For example, R may be ahydrocarbylene group having about 6 to about 25 carbons, preferablyabout 6 to about 12 carbon atoms. In another embodiment, R isunsubstituted or substituted. For example, in some cases, the cyclic oraromatic group(s) may be substituted at the 2-, 3-, and/or 4-positions,or at the ortho-, meta-, and/or para-positions, respectively.Substituted groups may include, but are not limited to, halogens,primary, secondary, or tertiary hydrocarbon groups, or a mixturethereof.

[0090] Because light stability of the compositions of the invention maybe accomplished in a variety of ways for the purposes of thisapplication, i.e., through the use of saturated components, lightstabilizers, whitening agents, or a mixture thereof, the isocyanate usedin the prepolymer may be saturated, semi-saturated, unsaturated, or amixture thereof. For example, isocyanates for use with the presentinvention include aliphatic (saturated), cycloaliphatic, aromaticaliphatic (semi-saturated), aromatic (unsaturated), any derivativesthereof, and combinations of these compounds having two or moreisocyanate (NCO) groups per molecule. The term “saturated,” as usedherein, refers to compositions having saturated aliphatic and alicyclicpolymer backbones, i.e., with no carbon-carbon double bonds. As usedherein, aromatic aliphatic compounds should be understood as thosecontaining an aromatic ring, wherein the isocyanate group is notdirectly bonded to the ring. One example of an aromatic aliphaticcompound is a tetramethylene diisocyanate (TMXDI).

[0091] The isocyanates may be organic polyisocyanate-terminatedprepolymers, low free isocyanate prepolymer, and mixtures thereof. Theisocyanate-containing reactable component may also include anyisocyanate-functional monomer, dimer, trimer, or polymeric adductthereof, prepolymer, quasi-prepolymer, or mixtures thereof.

[0092] Examples of isocyanates that can be used with the presentinvention include, but are not limited to, substituted and isomericmixtures including 2,2′-, 2,4′-, and 4,4′-diphenylmethane diisocyanate(MDI); 3,3′-dimethyl-4,4′-biphenylene diisocyanate (TODI); toluenediisocyanate (TDI); polymeric MDI; carbodiimide-modified liquid4,4′-diphenylmethane diisocyanate; para-phenylene diisocyanate (PPDI);meta-phenylene diisocyanate (MPDI); triphenyl methane-4,4′- andtriphenyl methane-4,4″-triisocyanate; naphthylene-1,5-diisocyanate;2,4′-, 4,4′-, and 2,2-biphenyl diisocyanate; polyphenylene polymethylenepolyisocyanate (PMDI) (also known as polymeric PMDI); mixtures of MDIand PMDI; mixtures of PMDI and TDI; ethylene diisocyanate;propylene-1,2-diisocyanate; tetramethylene-1,2-diisocyanate;tetramethylene-1,3-diisocyanate; tetramethylene-1,4-diisocyanate;1,6-hexamethylene diisocyanate (HDI); octamethylene diisocyanate;decamethylene diisocyanate; 2,2,4-trimethylhexamethylene diisocyanate;2,4,4-trimethylhexamethylene diisocyanate; dodecane-1,12-diisocyanate;dicyclohexylmethane diisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,2-diisocyanate; cyclohexane-1,3-diisocyanate;cyclohexane-1,4-diisocyanate; methylcyclohexylene diisocyanate (HTDI);2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane diisocyanate;4,4′-dicyclohexyl diisocyanate; 2,4′-dicyclohexyl diisocyanate;1,3,5-cyclohexane triisocyanate; isocyanatomethylcyclohexane isocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane;isocyanatoethylcyclohexane isocyanate; bis(isocyanatomethyl)-cyclohexanediisocyanate; 4,4′-bis(isocyanatomethyl) dicyclohexane;2,4′-bis(isocyanatomethyl) dicyclohexane; isophorone diisocyanate(IPDI); triisocyanate of HDI; triisocyanate of2,2,4-trimethyl-1,6-hexane diisocyanate (TMDI); 4,4′ dicyclohexylmethanediisocyanate (H12MDI); 2,4-hexahydrotoluene diisocyanate;2,6-hexahydrotoluene diisocyanate; 1,2-, 1,3-, and 1,4 -phenylenediisocyanate; aromatic aliphatic isocyanate, such as 1,2-, 1,3-, and1,4-xylene diisocyanate; meta-tetramethylxylene diisocyanate (m-TMI);para-tetramethylxylene diisocyanate (p-TMXDI); trimerized isocyanurateof any polyisocyanate, such as isocyanurate of toluene diisocyanate,trimer of diphenylmethane diisocyanate, trimer of tetramethylxylenediisocyanate, isocyanurate of hexamethylene diisocyanate, and mixturesthereof; dimerized uretdione of any polyisocyanate, such as uretdione oftoluene diisocyanate, uretdione of hexamethylene diisocyanate, andmixtures thereof; modified polyisocyanate derived from the aboveisocyanates and polyisocyanates; and mixtures thereof.

[0093] Of the list above, the following isocyanates are saturated:ethylene diisocyanate; propylene-1,2-diisocyanate; tetramethylenediisocyanate; tetramethylene-1,4-diisocyanate; 1,6-hexamethylenediisocyanate (HDI); octanethylene diisocyanate; decamethylenediisocyanate; 2,2,4-trimethylhexamethylene diisocyanate;2,4,4-trimethylhexamethylene diisocyanate; dodecane-1,12-diisocyanate;dicyclohexylmethane diisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,2-diisocyanate; cyclohexane-1,3-diisocyanate;cyclohexane-1,4-diisocyanate; methylcyclohexylene diisocyanate (HTDI);2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane diisocyanate;4,4′-dicyclohexyl diisocyanate; 2,4′-dicyclohexyl diisocyanate;1,3,5-cyclohexane triisocyanate; isocyanatomethylcyclohexane isocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane;isocyanatoethylcyclohexane isocyanate; bis(isocyanatomethyl)-cyclohexanediisocyanate; 4,4′-bis(isocyanatomethyl) dicyclohexane;2,4′-bis(isocyanatomethyl) dicyclohexane; isophorone diisocyanate(IPDI); triisocyanate of HDI; triisocyanate of2,2,4-trimethyl-1,6-hexane diisocyanate (TMDI); 4,4′-dicyclohexylmethanediisocyanate (H12MDI); 2,4-hexahydrotoluene diisocyanate;2,6-hexahydrotoluene diisocyanate; and mixtures thereof. Aromaticaliphatic isocyanates may also be used to form light stable materials.Examples of such isocyanates include 1,2-, 1,3-, and 1,4-xylenediisocyanate; meta-tetramethylxylene diisocyanate (m-TMXDI);para-tetramethylxylene diisocyanate (p-TMXDI); trimerized isocyanurateof any polyisocyanate, such as isocyanurate of toluene diisocyanate,trimer of diphenylmethane diisocyanate, trimer of tetramethylxylenediisocyanate, isocyanurate of hexamethylene diisocyanate, and mixturesthereof; dimerized uretdione of any polyisocyanate, such as uretdione oftoluene diisocyanate, uretdione of hexamethylene diisocyanate, andmixtures thereof; a modified polyisocyanate derived from the aboveisocyanates and polyisocyanates; and mixtures thereof.

[0094] The Polyol or Polyamine

[0095] A polyurethane prepolymer is the reaction product of anisocyanate and a polyol. Exemplary polyols include, but are not limitedto, polyether polyols, polycaprolactone polyols, polyester polyols,polycarbonate polyols, hydrocarbon polyols, and mixtures thereof. Bothsaturated and unsaturated polyols are suitable for use with the presentinvention.

[0096] Suitable polyether polyols for use in the present inventioninclude, but are not limited to, polytetramethylene ether glycol(PTMEG); copolymer of polytetramethylene ether glycol and2-methyl-1,4-butane diol (PTG-L); poly(oxyethylene)glycol;poly(oxypropylene)glycol; ethylene oxide capped(polyoxypropylene)glycol; poly (oxypropylene oxyethylene)glycol; andmixtures thereof.

[0097] Suitable polycaprolactone polyols include, but not limited to,diethylene glycol initiated polycaprolactone; propylene glycol initiatedpolycaprolactone; 1,4-butanediol initiated polycaprolactone; trimethylolpropane initiated polycaprolactone; neopentyl glycol initiatedpolycaprolactone; 1,6-hexanediol initiated polycaprolactone;polytetramethylene ether glycol (PTMEG) initiated polycaprolactone;ethylene glycol initiated polycaprolactone; dipropylene glycol initiatedpolycaprolactone; and mixtures thereof.

[0098] Suitable polyester polyols include, but not limited to,polyethylene adipate glycol; polyethylene propylene adipate glycol;polybutylene adipate glycol; polyethylene butylene adipate glycol;polyhexamethylene adipate glycol; polyhexamethylene butylene adipateglycol; ortho-phthalate-1,6-hexanediol polyester polyol; polyethyleneterephthalate polyester polyols; and mixtures thereof.

[0099] Examples of polycarbonate polyols that may be used with thepresent invention include, but is not limited to, poly(phthalatecarbonate)glycol, poly(hexamethylene carbonate)glycol, polycarbonatepolyols containing bisphenol A, and mixtures thereof. Hydrocarbonpolyols include, but not limited to, hydroxy-terminated liquid isoprenerubber (LIR), hydroxy-terminated polybutadiene polyol,hydroxy-terminated polyolefin polyols, hydroxy-terminated hydrocarbonpolyols, and mixtures thereof. Other polyols that may be used to formthe prepolymer of the invention include, but not limited to, glycerols;castor oil and its derivatives; Polytail H; Polytail HA; Kraton polyols;acrylic polyols; acid functionalized polyols based on a carboxylic,sulfonic, or phosphoric acid group; dimer alcohols converted from thesaturated dimerized fatty acid; and mixtures thereof.

[0100] By using polyols based on a hydrophobic backbone, thepolyurethane compositions of the invention may be more water resistantthan those polyurethane compositions having polyols without ahydrophobic backbone. Some non-limiting examples of polyols based on ahydrophobic backbone include hydrocarbon polyols, hydroxy-terminatedpolybutadiene polyols, polyethers, polycaprolactones, and polyesters.

[0101] Polyurea prepolymers are the reaction product of anamine-terminated component and an isocyanate. Any amine-terminatedcompound available to one of ordinary skill in the art is suitable foruse in the polyurea prepolymer. The amine-terminated compound mayinclude amine-terminated hydrocarbons, amine-terminated polyethers,amine-terminated polyesters, amine-terminated polycarbonates,amine-terminated polycaprolactones, copolymers of polycaprolactone andpolyamines, amine-terminated polyamides, and mixtures thereof. Theamine-terminated segments may be in the form of a primary amine (NH₂) ora secondary amine (NHR).

[0102] Additional amine-terminated compounds useful in forming thepolyurea prepolymers of the present invention include, but are notlimited to, poly(acrylonitrile-co-butadiene);poly(1,4-butanediol)bis(4-aminobenzoate) in liquid or waxy solid form;linear and branched polyethylenimine; low and high molecular weightpolyethylenimine having an average molecular weight of about 500 toabout 30,000; poly(propylene glycol) bis(2-aminopropyl ether) having anaverage molecular weight of about 200 to about 5,000;polytetrahydrofuran bis(3-aminopropyl) terminated having an averagemolecular weight of about 200 to about 2000; and mixtures thereof, allof which are available from Aldrich of Milwaukee, Wis.

[0103] Blocking the Isocyanate Groups

[0104] As briefly mentioned above, the isocyanate groups in theprepolymer are preferably blocked as a result of the reaction of asuitable isocyanate with a blocking agent. The blocking agent may be anysuitable blocking agent that results in the prevention of prematurepolymerization or crosslinking of the isocyanate group(s) in theprepolymer.

[0105] Suitable blocking agents include, but are not limited to, linearand branched alcohols; phenols and derivatives thereof, such as xylenol;oximes, such as methyl ethyl ketoxime; lactams, such as ε-caprolactam;lactones, such as caprolactone; β-dicarbonyl compounds; hydroxamic acidesters; bisulfite addition compounds; hydroxylamines; esters ofp-hydroxybenzoic acid; N-hydroxyphthalimide; N-hydroxysuccinimide;triazoles; substituted imidazolines; tetrahydropyrimidines;caprolactones; and mixtures thereof. In one embodiment, the blockingagent is selected from the group consisting of phenols, branchedalcohols, methyl ethyl ketoxime, ε-caprolactam, ε-caprolactone, andmixtures thereof.

[0106] In this aspect of the invention, preferably greater than about 80percent of the isocyanate radicals are blocked, and more preferablyabout 90 percent or greater of the isocyanate radicals are blocked. Inone embodiment, about 95 percent or more of the isocyanate radicals areblocked. In another embodiment, about 97 percent or more of theisocyanate radicals are blocked. In still another embodiment,substantially all of the isocyanate radicals are blocked.

[0107] The blocked isocyanate compound is stable at room temperature asa carbamic acid compound free of isocyanate radicals capable ofliberating at room temperature. When heated, or reacted with a“deblocking” agent, the isocyanate radicals are activated, i.e.,deblocked and dissociated. For example, in one embodiment, theisocyanate group(s) is blocked with ε-caprolactone. The ε-caprolactonevolatilizes at a temperature of approximately 300° F., exposing thepolyisocyanate groups for crosslinking.

[0108] The reaction of the isocyanate and blocking agent may beaccomplished in any suitable way that results in a blocked prepolymer.For example, the isocyanate groups may be blocked after the prepolymeris formed. One example of such a blocking mechanism using a polyureaprepolymer is shown below:

[0109] where R and R₁ may be independently any straight or branchedhydrocarbon moiety, acyclic group, cyclic group, heterocyclic group,aromatic group, phenyl group, hydrocarbylene group, or a mixturethereof.

[0110] In particular, a blocked polyurea prepolymer may be formed byfirst reacting a polyamide-based amine and an excess of isocyanate toform a polyamide-based polyurea prepolymer and then blocking theprepolymer with a phenol to form a blocked polyamide-based polyureaprepolymer. The general reaction scheme is as follows:

[0111] where R may be independently any straight or branched hydrocarbonmoiety, acyclic group, cyclic group, heterocyclic group, aromatic group,phenyl group, hydrocarbylene group, or a mixture thereof.

[0112] A blocked polyurethane prepolymer may be formed in a similarmanner, using a hydroxy-terminated component in place of theamine-terminated component. A general reaction scheme is shown below:

[0113] where R and R₁ may be independently any straight or branchedhydrocarbon moiety, acyclic group, cyclic group, heterocyclic group,aromatic group, phenyl group, hydrocarbylene group, or a mixturethereof.

[0114] The blocking mechanism may also be performed prior to theformation of the prepolymer. For example, a diisocyanate havingisocyanate radicals with different reactivities, such as 2,4-toluenediisocyanate, may be used to form a half-blocked intermediate. Thehalf-blocked intermediate is then reacted with an amine-terminatedcomponent to form a polyurea prepolymer or a polyol to form apolyurethane prepolymer. The blocking agent used to form thehalf-blocked intermediate may be any suitable blocking agent. Onespecific example includes the use of equal parts of 2-ethylhexanol and2,4-toluene diisocyanate.

[0115] In addition, commercially available urethane and urea elastomerswith blocked isocyanate groups are contemplated for use as the firstpolymeric system of the invention. For example, ADIPRENE® BL-16,commercially available from Crompton Corporation of Middlebury, Conn.,is a liquid urethane elastomer with blocked isocyanate curing sites thatcan be activated by heating. The blocking agent is methyl ethylketoxime. The free isocyanate content is less than 0.25 percent byweight.

[0116] The Curing Agent

[0117] The prepolymers of the present invention may be cured with ahydroxy-terminated curing agent, an amine-terminated curing agent, or amixture or hybrid thereof, which may include one or more saturated,unsaturated, aromatic, and cyclic groups. Additionally, thehydroxy-terminated and amine-terminated curatives may include one ormore halogen groups.

[0118] “Curing agents,” as used herein, means any compound, orcombination thereof, capable of connecting at least two polymeric oroligomeric chains, precursors, or macromonomers together underappropriate circumstances. For example, in step-growth or condensationpolymers, e.g., such as the polyurethane-based or polyurea-based systemsof the present invention, a curing agent may serve to build the linearmolecular weight of a single polymer molecule, to create, e.g., acrosslinked urethane/urea network, or both. As another example, inepoxy-based systems such as the second polymeric system discussed inmore detail below, a curing agent may simultaneously or sequentiallyfacilitate polymerization and network formation. In most other types ofpolymers, frequently formed through addition polymerization, curingagents serve only to crosslink polymers that have already been fully ordesirably polymerized. For the purposes of this disclosure, curingagents may also be referred to as either “chain extenders,”“crosslinkers,” or both.

[0119] As discussed above, however, the selection of the type ofprepolymer and curing agent determines the type of linkages present inthe first polymeric system. For example, when a hydroxy-terminatedcuring is used as a curing agent for a polyurea-based prepolymer, theresulting system will contain urethane linkages as a result of theexcess isocyanate reacting with the hydroxy groups of the curing agentand is referred to as a polyurea-urethane system as opposed to a purepolyurea system, which contains only urea linkages. Similarly, apolyurethane prepolymer cured with an amine-terminated curing agent willproduce a system including both urethane and urea linkages and isreferred to as a polyurethane-urea system.

[0120] Suitable hydroxy-containing curing agents have a molecular weightof about 50 to about 4,000, and include, but are not limited to,unsaturated diols, such as:

[0121] 1) 1,3-bis(2-hydroxyethoxy)benzene;1,3-bis[2-(2-hydroxyethoxy)ethoxy]benzene;1,3-bis{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene;

[0122] 2) N,N-bis(β-hydroxypropyl)aniline;

[0123] 3) hydroquinone-di(β-hydroxyethyl)ether;resorcinol-di(β-hydroxyethyl)ether;

[0124] 4) ethoxylates of the bis-phenols; bis(2-hydroxyethyl)bisphenol;and

[0125] 5) tetramethylxylylene diols; xylene glycol,

[0126] saturated diols, such as:

[0127] 1) ethylene glycol; diethylene glycol; polyethylene glycol;propylene glycol; dipropylene glycol; polypropylene glycol;2-methyl-1,3-propanediol; 1,2-, 1,3-, 1,4-, or 2,3-butanediols;2-methyl-1,4-butanediol; 2,3-dimethyl-2,3-butanediol; 1,5-pentanediol;neopentyl glycol; 1,6-hexanediol; trimethylolpropane;

[0128] 2) cyclohexyldimethylol;

[0129] 3) 1,3-bis(2-hydroxyethoxy)cyclohexane;1,3-bis[2-(2-hydroxyethoxy)ethoxy]cyclohexane; 1,3-bis{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy} cyclohexane; and

[0130] 4) PTMEG having a molecular weight of about 200 to about 4000,unsaturated triols, such as castor oil (a.k.a. triricinoleoyl glycerol),saturated triols, such as 1,2,4-butanetriol; 1,2,6-hexanetriol;trimethylolethane (a.k.a. 1,1,1-tri(hydroxymethyl)ethane);trimethylolpropane (a.k.a. 2,2-di(hydroxymethyl)-1-butanol);triethanolamine; and triisopropanolamine, unsaturated tetraols, such as2-propanol-1,1′-phenylaminobis and2,4,6-tris(N-methyl-N-hydroxymethyl-aminomethyl)phenol, saturatedtetraols, such as pentaerythritol (a.k.a. tetramethylolmethane); andtetrahydroxypropylene ethylenediamine (a.k.a.N,N,N′,N′-tetrakis(2-hydroxypropyl)-ethylenediamine), and other polyolssuch as mannitol (a.k.a. 1,2,3,4,5,6-hexanehexol) and sorbitol (anenantiomer of mannitol) (both saturated).

[0131] Suitable amine-containing curing agents may have a molecularweight of about 50 to about 5,000, and include, but are not limited to,unsaturated diamines, such as:

[0132] 1) m-phenylenediamine; o-phenylenediamine; p-phenylenediamine;2,4- and 2-6-toluene diamine; 1,2-, 1,3-, or1,4-bis(sec-butylamino)benzene (Unilink 4100);3,3′-dimethyl-4,4′-biphenylene diamine; 1,2-, 1,3-, or1,4-bis(sec-butylamino) xylene;

[0133] 2) 3,5-diethyl-(2,4- or 2,6-)toluenediamine;3,5-dimethylthio-(2,4- or 2,6) toluenediamine; 3,5-diethylthio-(2,4- or2,6-)toluenediamine;

[0134] 3) 4,4′-diamino-diphenylmethane (a.k.a. 4,4′-methylene-dianilineor “MDA”); 3,3′-dimethyl-4,4′-diamino-diphenylmethane;3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-diphenylmethane (a.k.a.4,4′-methylene-bis(2-ethyl-6-methyl-benezeneamine));3,3′-dichloro-4,4′-diamino-diphenylmethane (a.k.a.4,4′-methylene-bis(2-chloroaniline) or “MOCA”);3,3′-diethyl-5,5′-dichloro-4,4′-diamino-diphenylmethane;3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (a.k.a.4,4′-methylene-bis(2,6-diethylaniline) or “MDEA”);2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (a.k.a.4,4′-methylene-bis(3-chloro-2,6-diethyleneaniline) or “MCDEA”);3,3′-dichloro-4,4′-diamino-diphenylmethane;2,2′,3,3′-tetrachloro-4,4′-diamino-diphenylmethane (a.k.a.4,4′-methylene-bis(2,3-dichloroaniline) or “MDCA”);3,3′-dichloro-2,2′,6,6′-tetraethyl-4,4′-diaminodiphenylmethane;4,4′-bis-(sec-butylamino)-diphenylmethane (Unilink 4200);3,3′-dimethyl-4,4′-bis-(sec-butylamino)-diphenylmethane;N,N′-dialkylamino-diphenylmethane;3,3′,5,5′-tetraisopropyl-4,4′-diaminodiphenylmethane;3,3′-dimethyl-5,5′-diisopropyl-4,4′-diaminodiphenylmethane;3,3′-diethyl-5,5′-diisopropyl-4,4′-diaminodiphenylmethane;3,3′-dimethyl-5,5′-di-t-butyl-4,4′-diaminodiphenylmethane; isomersthereof;

[0135] 4) trimethyleneglycol-di(p-aminobenzoate);polyethyleneglycol-di(p-aminobenzoate);polytetramethyleneglycol-di(p-aminobenzoate);

[0136] 5) 2,3,5,6-tetramethyl-1,4-diaminobenzene; and

[0137] 6) m-xylene diamine; m-tetramethylxylene diamine,

[0138] saturated diamines, such as:

[0139] 1) ethylene diamine; 1,3-propylene diamine;2-methyl-pentamethylene diamine; 1,3-pentanediamine; hexamethylenediamine; 2,2,4- and 2,4,4-trimethyl-1,6-hexane diamine;

[0140] 2) imino-bis(propylamine); methylimino-bis(propylamine) (a.k.a.N-(3-aminopropyl)-N-methyl-1,3-propanediamine); 1,12-dodecanediamine;

[0141] 3) 1,4-bis(3-aminopropoxy)butane (a.k.a.3,3′-[1,4-butanediylbis-(oxy)bis]-1-propanamine);diethyleneglycol-bis(propylamine) (a.k.a.diethyleneglycol-di(aminopropyl)ether);4,7,10-trioxatridecane-1,13-diamine; polyoxyethylene diamines;polyoxypropylene diamines; (ethylene oxide capped)-polyoxypropyleneether diamines; polytetramethylene ether diamines;

[0142] 4) 1,4-diamino-cyclohexane; 1,3-diamino-cyclohexane;1,2-diamino-cylcohexane; 1,4-diaminoethylcyclohexane;1-methyl-3,5-diethyl-2,4 (2,6)-diaminocyclohexane;1-methyl-3,5-dimethylthio-2,4 (2,6)-diaminocyclohexane;1-methyl-2,6-diamino-cyclohexane; 1,2-, 1,3-, or1,4-bis(methylamino)-cyclohexane; 1,2-, 1,3-, or1,4-bis(sec-butylamino)-cyclohexane; 1,2-, 1,3-, or1,4-bis(sec-butylamino methyl)-cyclohexane; isophorone diamine;

[0143] 5) 4,4′-diamino-dicyclohexylmethane;3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane;3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-dicyclohexylmethane;3,3′-dichloro-4,4′-diamino-dicyclohexylmethane;3,3′-diethyl-5,5′-dichloro-4,4′-diamino-dicyclohexylmethane;3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane (a.k.a.4,4′-methylene-bis(2,6-diethylaminocyclohexane));2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane;3,3′-dichloro-4,4′-diamino-dicyclohexylmethane;2,2′,3,3′-tetrachloro-4,4′-diamino-dicyclohexylmethane;3,3′-dichloro-2,2′,6,6′-tetraethyl-4,4′-dicyclohexylmethane;4,4′-bis(sec-butylamino)-dicyclohexylmethane (Clearlink® 1000);N,N′-dialkylamino-dicyclohexylmethane;3,3′-dimethyl-4,4′-bis(sec-butylamino)-dicyclohexylmethane (Clearlink®3000); N,N′-diisopropyl-isophorone diamine (Jefflink® 754);3-{[(5-amino-1,3,3-trimethylcyclohexyl)methyl]amino}-propanenitrile;N,N′-diethylmaleate-2-methyl-pentamethylene diamine (Desmophen® NH1220); N,N′-di(ethylmaleate-amino)-dicyclohexylmethane (Desmophen® NH1420); N,N′-di(ethylmaleate-amino)-dimethyl-dicyclohexylmethane(Desmophen® 1520); polyamine/carbonyl adducts;

[0144] 6) 1-methyl-3,5-dimethylthio-(2,4- or 2,6-)cyclohexyldiamine;1-methyl-3,5-diethyl-(2,4- or 2,6-)cyclohexyldiamine;

[0145] 7) N-aminoethylpiperazine; 1,2-, 1-3,1,4-bis-(isocyanatomethyl)cyclohexane;

[0146] 8) 2,3,5,6-tetramethyl-1,4-diaminocyclohexane;

[0147] 9) 3-bis-(1-amino-1-methylethyl)-cyclohexane (hydrogenatedversion of m-TMXDA);

[0148] triamines, such as diethylene triamine; dipropylene triamine;(propylene oxide)-based triamines (a.k.a. polyoxypropylene triamines);trimethylolpropane-based triamines, glycerin-based triamines,N-(2-aminoethyl)-1,3-propylenediamine (a.k.a. N₃-amine) (all saturated),tetramines, such as triethylene tetramine;N,N′-bis(3-aminopropyl)ethylenediamine (a.k.a. N₄-amine) (bothsaturated), and other polyamines, such as tetraethylene pentamine (alsosaturated).

[0149] Suitable amine-containing and hydroxy-containing hybrid curingagents may be monomeric, oligomeric, or polymeric, having at least onefree reactive hydroxyl group and at least one free reactive amine group.The hydroxyl and amine groups may be terminal or pendant groups on theoligomeric or polymeric backbone, and in the case of secondary aminegroups, may be embedded within the backbone. Non-limiting examples ofthe amine-containing and hydroxyl-containing hybrid curing agentsinclude monoethanolamine; monoisopropanolamine; diethanolamine; anddiisopropanolamine.

[0150] Saturated members of the above-listed curing agents arepreferably chosen to react with saturated prepolymers, i.e., thoseformed from saturated isocyanates and saturated polyols oramine-terminated polymers, to form a saturated polyurethane or polyureacomposition. Examples of saturated curatives include, but are notlimited to, 1,4-butanediol; ethylene glycol; diethylene glycol;polyethylene glycol; propylene glycol; dipropylene glycol; polypropyleneglycol; 2-methyl-1,3-propanediol; 2-methyl-1,4-butanediol;2,3-dimethyl-2,3-butanediol; 1,4-cyclohexyldimethylol; 1,2-butanediol;1,3-butanediol; 1,4-butanediol; 2,3-butanediol; trimethylolpropane;cyclohexyldimethylol; triisopropanolamine; diethylene glycolbis-(aminopropyl)ether; 1,5-pentanediol; 1,6-hexanediol;1,3-bis-(2-hydroxyethoxy)cyclohexane; 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]cyclohexane; 1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}cyclohexane; polytetramethylene ether glycol having molecular weightranging from about 250 to about 3900; ethylene diamine; hexamethylenediamine; 1-methyl-2,6-cyclohexyl diamine; 2,2,4- and2,4,4-trimethyl-1,6-hexanediamine;4,4′-bis-(sec-butylamino)-dicyclohexylmethane and derivatives thereof;1,4-bis-(sec-butylamino)-cyclohexane;1,2-bis-(sec-butylamino)-cyclohexane; 4,4′-dicyclohexylmethane diamine;1,4-cyclohexane-bis-(methylamine); 1,3-cyclohexane-bis-(methylamine);diethylene glycol bis-(aminopropyl) ether;2-methylpentamethylene-diamine; diaminocyclohexane; diethylene triamine;triethylene tetramine; tetraethylene pentamine; propylene diamine;dipropylene triamine; 1,3-diaminopropane; dimethylamino propylamine;diethylamino propylamine; imido-bis-(propylamine); monoethanolamine,diethanolamine; triethanolamine; monoisopropanolamine,diisopropanolamine; triisopropanolamine; isophoronediamine;N,N′-diisopropylisophorone diamine,3,3′-dimethyl-4,4′-bis(sec-butylamino)-dicyclohexylmethane, and mixturesthereof.

[0151] To further improve the shear resistance of the resultingelastomers, a trifunctional curing agent may also be used to helpimprove cross-linking. In such cases, a triol, such astrimethylolpropane, or a tetraol, such as N,N,N′,N′-tetrakis(2-hydroxylpropyl) ethylenediamine, may be added to thecurative blends. Useful triamine curing agents for improving thecrosslinking of polyurea elastomers include, but are not limited to:propylene oxide-based triamines; trimethylolpropane-based triamines;glycerin-based triamines; N,N-bis{2-[(aminocarbonyl)amino]ethyl}-urea;N,N′,N″-tris(2-aminoethyl)-methanetriamine;N1-(5-aminopentyl)-1,2,6-hexanetriamine; 1,1,2-ethanetriamine;N,N′,N″-tris(3-aminopropyl)-methanetriamine;N1-(2-aminoethyl)-1,2,6-hexanetriamine;N1-(10-aminodecyl)-1,2,6-hexanetriamine; 1,9,18-octadecanetriamine;4,10,16,22-tetraazapentacosane-1,13,25-triamine;N1-{3-[[4-[(3-aminopropyl)amino]butyl]amino]propyl}-1,2,6-hexanetriamine;di-9-octadecenyl-(Z,Z)-1,2,3-propanetriamine; 1,4,8-octanetriamine;1,5,9-nonanetriamine; 1,9,10-octadecanetriamine; 1,4,7-heptanetriamine;1,5,10-decanetriamine; 1,8,17-heptadecanetriamine; 1,2,4-butanetriamine;propanetriamine; 1,3,5-pentanetriamine; N1-{3-[[4-[(3-aminopropyl)amino]butyl]amino]propyl}-1,2,6-hexanetriamine; N1-{4-[(3-aminopropyl)amino]butyl}-1,2,6-hexanetriamine; 2,5-dimethyl-1,4,7-heptanetriamine;N1-(6-aminohexyl)-1,2,6-hexanetriamine;6-ethyl-3,9-dimethyl-3,6,9-undecanetriamine; 1,5,11-undecanetriamine;1,6,11-undecanetriamine; N,N-bis(aminomethyl)-methanediamine;N,N-bis(2-aminoethyl)-1,3-propanediamine; methanetriamine;N1-(2-aminoethyl)-N-2-(3-aminopropyl)-1,2,5-pentanetriamine;N1-(2-aminoethyl)-1,2,6-hexanetriamine;2,6,11-trimethyl-2,6,11-dodecanetriamine; 1,1,3-propanetriamine;6-(aminomethyl)-1,4,9-nonanetriamine; 1,2,6-hexanetriamine;N2-(2-aminoethyl)-1,1,2-ethanetriamine; 1,3,6-hexanetriamine;N,N-bis(2-aminoethyl)-1,2-ethanediamine;3-(aminomethyl)-1,2,4-butanetriamine; 1,1,1-ethanetriamine;N1,N1-bis(2-aminoethyl) 1,2-propanediamine; 1,2,3-propanetriamine;2-methyl-1,2,3-propanetriamine; and mixtures thereof.

[0152] In one embodiment, the curing agent is a blocked, delayed actioncurative that reacts slowly with the terminal isocyanate groups at roomtemperature. When the blocked, delayed action curative is heated to anelevated temperature, the curative rapidly cures the urethane or ureaelastomer. In this aspect of the invention, the blocked, delayed actioncurative can include a salt complex that deblocks at an elevatedtemperature. The deblocking temperature may be any suitable elevatedtemperature that results in freeing the curing agent. For example, thedeblocking temperature used to activate the curing process can be fromabout 175° F. to about 350° F., from about 185° F. to about 325° F.,from about 195° F. to about 315° F., or from about 205° F. to about 305°F.

[0153] One example of a suitable blocked, delayed action curative foruse with the first polymeric system is CAYTUR® 21, which is commerciallyavailable from Crompton Corporation of Middlebury, Conn. CAYTUR® 21 is ablocked, delayed action diamine curative that is used primarily withurethane elastomer prepolymers based on toluene diisocyanate andpolyether polyols. It consists of a complex of methylene dianiline (MDA)and sodium chloride dispersed in dioctyl phthalate, wherein the saltcomplex deblocks at a temperature ranging from 212° F. to 302° F.

[0154] In another embodiment, the curing agent is a modified curativeblend as disclosed in co-pending U.S. Patent Publication No.2003/0212240, which is incorporated by reference herein in its entirety.For example, the curing agent of the invention may be modified with afreezing point depressing agent to create a curative blend with a sloweronset of solidification and with storage stable pigment dispersion. Thefreezing point depressing agent is preferably added in an amountsufficient to reduce the freezing point of the curing agent by asuitable amount to prevent loss of pigment dispersion, but not affectthe physical properties of the golf ball. Thus, a curative blendaccording to the present invention may include a polyamine adduct and afreezing point depressing agent.

[0155] The Second Polymeric System

[0156] The second system included in the IPN of the invention may bebased on an epoxy or an acrylic resin. The epoxy-based system is curedwith a curing agent/catalyzing agent, whereas the acrylic-based systemrequires an initiator for polymerization. The particulars of each systemare discussed in more detail below, however, the second polymeric systemis cured at the same time or substantially the same time as the firstpolymeric system in order to form the IPN.

[0157] The Epoxy System

[0158] Any cured epoxy resin is suitable for use as the second polymericsystem in the IPN of the present invention. Suitable epoxy resinsinclude, but are not limited to, reaction products of bisphenol A andepichlorohydrin, reaction products of an aliphatic polyol andepichlorohydrin, and oxidized polyolefins. Examples of aliphatic polyolsinclude any of the saturated polyols discussed above with respect thefirst polymeric system. In one embodiment, the aliphatic polyol isglycerol. The oxidized polyolefins may be oxidized using any suitableacid, e.g., peracetic acid. In one embodiment, the epoxy resin is amodified epoxy resin including halogenated bisphenol. A commerciallyavailable bisphenol A epoxy resin is EPON®, a Jeffamine resinmanufactured by Huntsman Corporation of Austin, Tex.

[0159] In addition, epoxidized esters of unsaturated alcohols andunsaturated carboxylic acids are contemplated for use as the epoxyresin. In one embodiment, the epoxy resin includes at least one ofglycidyl glycidate; 2,3-epoxybutyl-3,4-epoxypentanoate;3,4-epoxy-3,4-epoxyhexyl; 3,4-epoxypentanoate; or mixtures thereof. Inanother embodiment, the second polymeric system include epoxidizedesters of unsaturated monohydric alcohols and polycarboxylic acids, suchas diglycidyl adipate; diglycidyl isophthalate; di(2,3-epoxybutyl)adipate; di(2,3-epoxybutyl)oxalate; di(2,3-epoxyhexyl) succinate;di(3,4-epoxybutyl) maleate; di(2,3-epoxyoctyl) pimelate;di(2,3-epoxybutyl) phthalate; di(2,3-epoxyoctyl)tetrahydrophthalate;di(4,5-epoxydodecyl) maleate; di(2,3-epoxybutyl) teraphthalate;di(2,3-epoxypentyl)thiodipropionate; di(5,6-epoxytetradecyl)diphenyldicarboxylate; di(3,4-epoxyheptyl)sulfonyldibutyrate;di(5,6-epoxypentadecyl) maleate; di(2,3-epoxybutyl) azelate;di(3,4-epoxybutyl) citrate; di(5,6-epoxyoctyl)cyclohexane-1,3-dicarboxylate; di(4,5-epoxyoctadecyl) malonate;tri(2,3-epoxybutyl)-1,2,4-butanetricarboxylate; and mixtures thereof.

[0160] Other examples of epoxy resins suitable for use with the presentinvention include, but are not limited to, epoxidized derivatives ofpolyethylenically unsaturated polycarboxylic acids; epoxidizedpolyesters that are the reaction product of an unsaturated polyhydricalcohol and/or an unsaturated polycarboxylic acid or anhydride groups;epoxidized polyethylenically unsaturated hydrocarbons; glycidyl ethersof novolac resins; and mixtures thereof.

[0161] The epoxy resin may be cured with a number of curingagents/catalyzing agents. In one embodiment, the curing agent is a Lewisbase, such as alkali metal hydroxide. Lewis bases are those compoundscontaining an atom with an unshared electron pair in its outer orbital.They are attracted to areas of reduced electron density in the moleculeswith which they react. The organic bases, such as tertiary amines(R₃N:), are representative of the more reactive-type Lewis basessuitable for curing epoxy resins.

[0162] In another embodiment, the curing agent is a Lewis acid, such asa phenol. In still another embodiment, the curing agent is an amine,such as tri(dimethylaminomethyl-phenol and dimethylaminomethylphenol. Inyet another embodiment, the curing agent is an amide, such asamidopolyamine.

[0163] The curing agent for the epoxy system may also be an anhydride.The anhydride may be alicylic, linear polymeric, aromatic, chlorinated,brominated, or mixtures thereof. Examples of suitable anhydrides to useas the curing agent include, but are not limited to, hexahydrophthalicanhydride, methyl hexahydrophthalic anhydride, dodecyl succinicanhydride, nadic methyl anhydride, and mixtures thereof. In oneembodiment, the anhydride is present in a blend or an adduct.

[0164] Those of ordinary skill in the art are familiar with the reactionmechanism of an epoxy resin and its curing agent. One example mechanism,using bisphenol A epoxy resin and a polyoxypropylene glycol based amine,is shown below:

[0165] The amines further react with the epoxy groups to build up themolecular weight of the epoxy system.

[0166] The amount of curing agent to epoxy resin is any suitable amountthat results in a completely cured epoxy system. For example, the curingagent to epoxy resin ratio may range from about 0.4 to about 1.4 (on anequivalent basis). In one embodiment, the curing agent to epoxy resinratio is about 0.6 to about 1.2. In another embodiment, the ratio ofcuring agent to epoxy resin is about 0.6 to about 1.0.

[0167] The Acrylic Resin System

[0168] The IPN of the present invention may also be formed using asecond polymeric system that is based on an acrylic resin. Inparticular, the acrylic resin system may be formed using an acrylatefunctional resin that is polymerized with an initiator.

[0169] Although some polymeric systems may be formed throughself-polymerization, for example, such as polystyrene from styrenemonomer, when activated by heat or the appropriate energy, most chaingrowth polymerizations involve an initiator. The choice of initiator ofuse in the present invention depends on each polymer component to besynthesized, and any available initiator capable of polymerizing theselected monomers, oligomers, or pre-polymers are generally also presentin a precursor package. Suitable initiators can include, for example,free radical, cationic initiators, or ionic initiators. In cases wherecommercially available initiators contain inhibitors, the inhibitors maybe separated and removed from the initiator by known methods prior touse.

[0170] Suitable initiators for use with the acrylic resin systeminclude, but are not limited to, benzoyl peroxide, t-amyl peroxide, andmixtures thereof.

[0171] Forming the IPN

[0172] The IPNs of the present invention include at least two precursorpackages, which correspond to the at least two polymeric systemsdescribed above. Each precursor package contains at least all thecompounds necessary to form one of the polymeric systems of the IPN.Compounds that may be used in a precursor package include any monomers,oligomers, or pre-polymers that are to be attached to the polymericsystem by polymerization.

[0173] For example, a precursor package for a first polymeric system mayinclude a blocked polyurethane or polyurea prepolymer, a chain extenderor curing agent, and, optionally, a “deblocking” agent. When referringto polymeric systems synthesized by step-growth polymerization, itshould be understood that monomers, oligomers, and pre-polymers refer toany or all compounds with functional groups that participate in thepolymerization and are attached to the resulting step-growth homopolymeror copolymer. A precursor package for the second polymeric system mayinclude an epoxy resin or acrylic resin and its respective curingagent/catalyzing agent/initiator.

[0174] Interpenetrating polymer networks according to the presentinvention may typically be fabricated by a number of different methodsknown to one of ordinary skill in the art. Such fabrication processesinclude, but are not limited to, the following groups of methods.

[0175] (1) At least two sets of pre-synthesized oligomeric or polymericcomponents are mixed together by any standard method or any method knownto one of ordinary skill in the art, such as, for example, melt mixing,solvating at least one component in a solution of at least one of theother components and a solvent or solvent mixture, or forming a solutionmixture from at least two solutions, each containing at least one set ofcomponents and a solvent or solvent mixture. In cases where solventmixing is involved, e.g., a coating composition including an IPN of thepresent invention, the majority of the solvent or solvent mixture shouldbe removed after mixing, for example, by evaporation, boiling,precipitation of the non-solvent components, or the like, preferablysuch that the IPN contains less than 10 percent solvent, or morepreferably is substantially free of solvent. The mixing process shouldallow for sufficiently intimate mixing of the components, for example,such that the at least two components are at least partiallyco-entangled. At least one of the at least two intimately mixedcomponents can then be crosslinked. If both components are to becrosslinked, the crosslinking can occur simultaneously or sequentially.

[0176] (2) At least one non-polymerized precursor package can beincorporated into at least one other pre-synthesized oligomeric orpolymeric component, which may or may not already be a crosslinkednetwork, which incorporation can occur by any method that facilitatesintimate mixing of the at least one precursor package with the at leastone pre-synthesized component, for example, such as by swelling the atleast one pre-synthesized component with the at least one precursorpackage, optionally under an applied pressure. Once the components areintimately mixed, the at least one precursor package can then beappropriately polymerized. In the event that the at least onepre-synthesized component is/are already crosslinked and a semi-IPN isdesired, a further crosslinking reaction may not be necessary.Otherwise, at least one component of the at least one precursor package,now polymerized, may be crosslinked. Alternately, at least one componentof the at least one precursor package may be crosslinked and polymerizedsimultaneously. If the at least one pre-synthesized component is/are notalready crosslinked, then the at least one pre-synthesized component andthe at least one polymerized precursor package component may becrosslinked simultaneously or sequentially. Alternately, if the at leastone pre-synthesized component is/are not already crosslinked and asemi-IPN is desired, at least one of either set of components can becrosslinked.

[0177] (3) The at least two precursor packages can be mixed together byany method that facilitates intimate mixing of the compounds in the atleast two precursor packages. The at least two intimately mixedprecursor packages can then be polymerized and/or crosslinked in anyorder to form an IPN of the present invention. In one embodiment, the atleast two precursor packages can be polymerized simultaneously orsequentially, but not crosslinked, yielding an intimately mixed blend ofthe at least two polymerized precursor package components. Then, one ormore of the polymerized components can be crosslinked by an appropriatecrosslinking method, and, if more than one of the polymerized componentsare to be crosslinked, the crosslinking can be done simultaneously orsequentially. Alternately, for one or more of the polymerizedcomponents, the crosslinking reaction may occur simultaneously with thepolymerization reaction. In another embodiment, at least one of the atleast two intimately mixed precursor packages can be polymerized andcrosslinked in the presence of the other precursor package(s), afterwhich the subsequent steps are similar to method #2 (after the initialintimate mixing).

[0178] It should be understood that certain rapid-forming IPN systemsmay need to be prepared using a quick-forming process, such as reactioninjection molding (RIM), which is a processing method known for use informing articles or materials out of rapidly curing polymer systems.Thus, the faster the formation of a given IPN system, the more suitablethe use of RIM to process it. Indeed, if the IPN gelation time is lessthan about 60 seconds, preferably less than about 30 seconds, RIM ispreferred over other conventional processing techniques. In the RIMprocess, at least two or more reactive, low-viscosity, liquid componentsare generally mixed, for example, by impingement, and injected underhigh pressure (e.g., at or above about 1200 psi) into a mold. Thereaction times for RIM systems are much faster than in conventionallower-pressure mixing and metering equipment. The precursor packagesused for the RIM process, therefore, are typically much lower inviscosity to better facilitate intimate mixing in a very short time.

[0179] (4) Each of the at least two precursor packages can be at leastpartially polymerized separately, and preferably simultaneously, atwhich point the at least partially polymerized precursor packages can bemixed together in a manner sufficient to result in intimate mixing ofthe components of the at least two, at-least-partially-polymerizedcomponents. In some urethane-epoxy systems, the total gelation time mayrange from about 40 to 100 seconds. The remainder of the polymerizationsof the intimately mixed components then occur simultaneously, althoughone polymerization may be sufficiently complete before any other. Then,after all polymerizations are sufficiently complete, one or more of thepolymerized components can be crosslinked by an appropriate crosslinkingmethod, and, if more than one of the polymerized components are to becrosslinked, the crosslinking can be done simultaneously orsequentially. Alternately, for one or more of the polymerizedcomponents, the crosslinking reaction may occur simultaneously with thepolymerization reaction.

[0180] In one embodiment, the precursor packages are mixed separatelyuntil a sufficient viscosity is attained, preferably from about 2,000cPs to 35,000 cPs, more preferably from about 8,000 cPs to 30,000 cPs,most preferably from about 15,000 cPs to 26,000 cPs.

[0181] When forming an IPN including an epoxy resin system, any of themethods above can be used. Generally, the blocked polyurea orpolyurethane prepolymer is mixed with its respective curing agent, e.g.,a short chain diol or diamine, the epoxy resin, and the epoxy curingagent/catalyzing agent. The addition of heat, or a “deblocking” agent,is used to deblock the isocyanate groups, which react with the curingagent, and form urethane linkages or urea linkages depending on the typeof curing agent used. The epoxy system simultaneously or sequentiallyreacts with its curing agent/catalyzing agent to form a cured epoxysystem. In one embodiment, the IPN includes at least about 50 percent byweight of the polyurethane system, preferably about 80 percent orgreater, more preferably about 90 percent or greater

[0182] In the case where at least one of the polymeric systems is athermoset material, the mixture of the two systems can be made in anumber of ways, such as by grinding a cured epoxy polymer into a powder;mixing the proper proportion of the powdered epoxy polymer with thepolyurethane or polyurea prepolymer to uniformly disperse the epoxypowder, but before polymerization, gelation, or solidification occurs;and shaping the mixture into a golf equipment component (e.g., a golfall or portion thereof).

[0183] When forming an IPN of the invention that includes an acrylicresin, the blocked polyurethane or polyurea prepolymer is mixed with itsrespective curing agent, e.g., a short chain diol or diamine, anacrylate resin, and an initiator. As with the epoxy-based IPN, once thetemperature is high enough to deblock the isocyanate groups in theprepolymer, urethane or urea linkages form (depending on the curingagent selected) to form the first system while the acrylatepolymerization is initiated to form the second system. In thealternative, a “deblocking” agent may be used instead of, or incombination with, raising the temperature to deblock the isocyanategroups in the prepolymer. Once the isocyanate groups are deblocked,however, the IPN forms as the first and second polymeric systems curesimultaneously or sequentially. In one embodiment, an IPN according tothe invention may include an acrylate homopolymer or copolymer or ahomopolymer or copolymer containing a conjugated diene, especiallypolybutadiene, but may not include both.

[0184] If heat is used to deblock the isocyanate groups, the temperaturerequired to expose the isocyanate groups is dependent on the type ofblocking agent. A catalyst may be used to lower the deblockingtemperature. Suitable catalysts include, but are not limited to,organometallic compounds, tertiary amines, quaternary ammonium salts,and combinations thereof. For example, dibutyltin dilaurate, dibutyltindiacetate, zinc naphthenate, lead naphthenate, bismuth salts, titanates,Co, Mg, Sr, and Ba salts of hexanoic, octanoic, naphthenic, andlinolenic acids, metal acetylacetonates, and mixtures thereof arecontemplated as catalysts for the deblocking mechanism. In oneembodiment, a combination of organotin compounds and quaternary ammoniumsalts are used for catalysis to lower the deblocking temperature.

[0185] Crosslinking agents for each of the polymeric systems may beincluded in the precursor package to be mixed in with the systemsinitially, especially if they need to be externally activated, or may beadded subsequent to the intimate mixing step, especially to avoidpremature crosslinking by heating or exposure to activating energy orcompounds. If activation is needed for crosslinking one or more of theat least two intimately mixed components, it is typically performedafter an intimate mixing step. Activators for crosslinking may affect anagent or a part of the component itself, for example, such as acarbon-carbon double bond or a labile carbon-hydrogen bond, andgenerally include, but are not limited to, heat, light, UV radiation,x-rays, microwave radiation, and gamma radiation.

[0186] It should be understood that each method of crosslinking shouldbe chosen to match up with the choice of starting materials andpolymerization scheme used to synthesize each polymer system. It shouldalso be noted that each method of crosslinking should typically notsignificantly degrade or be counterproductive toward polymerization ornetwork formation of other components in the IPNs of the presentinvention.

[0187] A number of suitable polymerization and/or crosslinkingtechniques are contemplated to polymerize or crosslink the polymericsystems of the IPN. As used herein, the phrase “polymerization and/orcrosslinking techniques” refers to the optional use of one or moreinitiators in conjunction with the chosen radiation cure technique ortechniques. Thus, in one embodiment, the formation of an IPN of thepresent invention includes polymerizing and/or crosslinking one or morepolymers, prepolymers, oligomers and/or monomers sequentially orsimultaneously using one or more polymerization and/or crosslinkingtechniques. In particular, the formation of an IPN includes sequentiallyor simultaneously exposing one or more polymers, prepolymers, oligomersand/or monomers to:

[0188] 1) an energy source selected from the group consisting ofthermal/heat (i.e., microwave or infrared), UV radiation, visibleradiation, electron beam radiation, x-ray radiation, gamma radiation,and combinations thereof, in the presence of an initiator; and

[0189] 2) optionally one or more additional energy sources selected fromthe group consisting of thermal/heat (i.e., microwave or infrared), UVradiation, visible radiation, electron beam radiation, x-ray radiation,gamma radiation, and combinations thereof, in the presence of aninitiator.

[0190] The initiator is optional and can be present or absent whenelectron beam radiation, x-ray radiation, thermal radiation, or gammaradiation is utilized in forming an IPN.

[0191] The energy source is selected such that its exposure to one ormore polymers, prepolymers, oligomers and/or monomers does not adverselyor detrimentally affect crosslinking and/or polymerization reactions orthe characteristics of the final crosslinked and/or polymerized IPN. Forexample, an IPN including polyurea and acrylate requires low temperaturefor a fast cure of polyurea prepolymer, but curing the acrylate systemgenerally requires heat, which adversely affects the curing of thepolyurea by reducing the reaction rate and cosmetically changing curedpolyurea. Electron beam radiation may be chosen to cure the acrylatebecause it can be utilized while avoiding the adverse or detrimentaleffects caused heat.

[0192] In one embodiment, the one or more additional energy source iselectron beam radiation. In particular, the formation of an IPN includessequentially or simultaneously exposing one or more polymers,prepolymers, oligomers and/or monomers to:

[0193] 1) an energy source selected from the group consisting of thermalradiation/heat, UV radiation, visible radiation, electron beamradiation, x-ray radiation, gamma radiation, and combinations thereof;and

[0194] 2) electron beam radiation.

[0195] The use of a low power electron beam source allows more efficientdosage of electrons and also helps prevent unwanted reactions with thefinal crosslinked/polymerized IPN.

[0196] The electron beam tube is a vacuum tube having a base end and awindow end. An extended filament is disposed within the beam tubeproximate to the base end. The filament generates electrons inconjunction with electron beam forming electrodes. The electrons fromthe filament (i.e., electron beam source) are directed toward andthrough the beam window of the electron beam tube. A low power electronbeam tube is preferred. The beam energy from a low power beam tube isbelow about 125 kV (kilovolts), typically between about 15-80 kV (or anyvalue therebetween), more typically between about 20-75 kV and mosttypically between about 30-65 kV. The voltage to the power supply (inputvoltage from about 10 to about 1,000 volts) is preferably about 110volts (or less) and its operating power is preferably about 100 watts(or less). However, the output voltage of the beam tube may be between20-100 kV or any value therebetween. Likewise, the operating power ofthe electron beam may be from about 10-1,000 watts or any valuetherebetween.

[0197] The amount of time required for the systems to cure is variable,depending on the type of constituents in the two polymeric systems, thethickness of the material, the cure temperature, and other factors knownto those of skill in the art. In one embodiment, the cure time is about5 seconds to about 1 hour. In another embodiment, the cure time is about15 seconds to about 45 minutes, preferably about 30 seconds to about 30minutes. Alternatively, the cure time can be 1 hour or more. Forexample, the IPNs of the invention may be cured overnight at roomtemperature.

[0198] In addition, the amount of radiation energy needed tosufficiently initiate polymerization, cure, and/or crosslink thecomposition depends upon a number of factors including, for example, thechemical identity of the composition and precursors, as well as theinitiator, radiation source chosen, and length of exposure time of thepolymer components to the energy source. As discussed above, thermalradiative sources include infrared and microwave sources. Conditions forthermal or heat initiated polymerizations typically are from about 35°C. to about 300° C., preferably from about 50° C. to about 200° C. andfor a time of about fractions of minutes to about thousands of minutes.Examples of thermal free radical initiators include azo compounds,peroxides, persulfates (e.g., potassium persulfate, sodium persulfate,and ammonium persulfate), and redox initiators.

[0199] If actinic radiation is utilized, such as ultraviolet or visiblelight, a photoinitiator may be utilized. Upon being exposed toultraviolet or visible light, the photoinitiator generates a freeradical source or a cationic source. This free radical source orcationic source then initiates the polymerization. In free radicalprocesses, however, an initiator is optional when a source of electronbeam radiation, x-ray or gamma radiation energy is utilized. Thus, aninitiator may be present or absent when the energy source is electronbeam radiation, x-ray or gamma radiation energy. Gamma radiation andelectron beam radiation are useful because of their excellentpenetration at ambient temperature allows more control in the quiescentconditions. Gamma radiation and electron beam radiation are alsoadvantageous because they require minimal cooling of the cured inks (thecuring is done at ambient or room temperature), the ink are almostinstantaneously cured, obviate or reduce the need for costly ventilatingsystems, and, in the case of low power electron beam radiation, requirelow energy to cure. Additionally, curing by gamma radiation or electronbeam radiation allows the combination of several ink compositions in thesame curing cycle, which may not be possible for thermal curing becausethe different ink compositions may require different temperatures orcure times.

[0200] Suitable photoinitiators include, for example, those that absorbin the wavelength range from about 0.001 nm to 700 nm, preferably fromabout 100 nm to about 650 nm, more preferably from about 190 nm to about600 nm. Photoinitiators include peroxides, azo compounds, quinines(e.g., substituted and unsubstituted anthraquinones, camphor quinone,alkyl-camphorquinone), benzophenones (e.g., 4-methylbenzophenone,benzophenone, 4,4′-bisdimethylamine-benzophenone, 1-hydroxycyclohexylphenyl ketone), nitroso compounds, acyl halides, hydrazones, mercaptocompounds, pyrylium compounds, triacylimidazoles, organophosphoruscompounds (e.g., acylphosphine oxides,2,4,6-trimethylbenzoyldiphenylphosphine oxide), bisimidazoles,chloroalkyltriazines, benzoates (e.g., ethyl 4-(dimethylamino)benzoate),benzoyl compounds (e.g., acrylic or methacrylic[(2-alkoxy-2-phenyl-2-benzoyl)ethyl]esters, 4-benzoyl-4′-methyldiphenylsulfide, 1-benzoylcyclohexanol), benzoin ethers (e.g., substituted andunsubstituted C₁-C₈ alkyl benzoin ethers, such as benzoisobutyl ether),benzil ketals (e.g., benzyldimethyl ketal), thioxanthones (e.g.,2-isopropylthioxanthone and 4-isopropylthioxanthone), acetophenonederivatives (e.g., 2,2-dimethoxy-2-phenyl-acetophenone,2,2-diethoxyacetophenone, 2,2-diacetoxyacetophenone, chlorinatedacetophenone, hydroxyacetophenone), ketones (e.g.,2-methyl-1-(4-[methylthio]phenyl)-2-(4-morpholinyl)-1-propanone,2-hydroxy-2-methyl-1-phenylpropan-1-one, 4-(2-hydroxyethoxy)phenyl2-hydroxy-2-propyl ketone,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)furan-1-one),metallocenes (e.g., Group VIII metallocenes, perfluorinateddiphenyltitanocenes), hexafluorophosphate salts (e.g.,(η⁵-cyclopentadienyl)(η⁶-isopropylphenyl)iron(II)hexafluorophosphate,triphenylsulfonium hexafluorophosphate), sulfonium salts, diacrylates(e.g., butanediol diacrylate, dipropylene glycol diacrylate, hexanedioldiacrylate, 4-(1,1-dimethylethyl)cyclohexyl acrylate, trimethylolpropanetriacrylate and tripropylene glycol diacrylate), polyols (e.g.,polyethylene glycol), pyrollidones (e.g., N-vinyl pyrollidone) andmixtures thereof.

[0201] Examples of commercially available photoinitiators include, butare not limited to, Vicure 10, 30 (made by Stauffer Chemical), Irgacure184, 651, 2959, 907, 369, 1700, 1800, 1850, 819 (made by Chiba SpecialtyChemicals), Darocurel 173 (made by EM Chemical), Quantacure CTX, ITX(made by Aceto Chemical), Lucirin TPO (made by BASF). Other examples ofsuitable photoinitiators are described in, for example, U.S. Pat. No.6,500,495, the entirety of which is incorporated herein by reference.

[0202] Cationic initiators include Group IA or Group IIA organocompounds, aryl sulfonium salts, hexafluorometallic salts, Bronstedacids, Lewis acids or mixtures thereof. In particular, cationicinitiators include sec-butyllithium, n-butyllithium, other(C₁-C₁₀)alkyllithiums, aryllithiums, sulfonic acids (e.g. sulfuricacid), phosphoric acid, perchloric acid, triflic acid, BF₃, aluminumhalides (e.g., AlC1 ₃, AlBr₃), triarylsulfonium salts, diaryliudoniumsalts or mixtures thereof.

[0203] Peroxide and organic peroxide initiators typically are R—O—O—R₁,wherein R and R₁ are each independently selected from the groupconsisting of hydrogen, (C₁-C₂₀)alkyl, (C₁-C₂₀)alkylene,(C₁-C₂₀)alkylyne, (C₁-C₂₀)cycloalkyl, and substituted or unsubstituted(C₆-C₂₄)aryl, wherein aryl may be phenyl, naphthyl, biphenyl, thienyl orpyridyl and the aryl moiety may in each case be mono- to trisubstitutedby F, Cl, Br, I, OH, CF₃, NO₂, CN, OCF₃, O—(C₁-C₁₀)alkyl, NH₂,NH(C₁-C₆)alkyl, COOH, COO(C₁-C₆)alkyl. As used herein, “substituted”refers to additional moieties or groups that are attached to and foundin R and R₁, which includes, but are not limited to F, Cl, Br, I, OH,CF₃, NO₂, CN, OCF₃, O—(C₁-C₁₀)alkyl, NH₂, NH(C₁-C₆)alkyl, COOH,COO(C₁-C₁₀)alkyl, (C₁-C₁₀)alkyl, (C₂-C₁₀)alkenyl, (C₂-C₁₀)alkynyl,(C₁-C₁₀)alkyl-COOH, (C₁-C₁₀)alkyl-aryl, wherein aryl may be phenyl,naphthyl, biphenyl, thienyl or pyridyl and the aryl moiety may in eachcase be mono-, di- or tri-substituted by F, Cl, Br, I, OH, CF₃, NO₂, CN,OCF₃, O—(C₁-C₁₀)alkyl, NH₂, NH(C₁-C₆)alkyl, COOH, COO(C₁-C₆)alkyl.

[0204] Examples of peroxide and organic peroxide initiators include, butare not limited to, di(2-tert-butyl-peroxyisopropyl)benzene peroxide orbis(tert-butylperoxy)diisopropylbenzene,2,5-di-(tert-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(tert-butylperoxy)valerate, lauryl peroxide,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, dicumyl peroxide,di-tert-butyl peroxide, di-tert-amyl peroxide, benzoyl-5-peroxide,tert-butyl hydroperoxide, benzoyl peroxide, acetyl peroxide, decanoylperoxide, dicetyl peroxydicarbonate, di(4-tert-butylcyclohexyl)peroxydicarbonate (available under the trade designation PERKADOX 16,from Akzo Chemicals, Inc., Chicago, Ill.), di(2-ethylhexyl)peroxydicarbonate, tert-butylperoxypivalate (available under the tradedesignation LUPERSOL 11, from Lucidol Division., Atochem North America,Buffalo, N.Y.) and tert-butylperoxy-2-ethylhexanoate (available underthe trade designation TRIGONOX 21-C50, from Akzo Chemicals, Inc.,Chicago, Ill.).

[0205] Azo compounds include, but are not limited to,4,4′-azobis(isobutyronitrile), 4,4′-azobis(cyanovalerate),4,4′-azobis(cyanovaleric acid),2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) (available under thetrade designation VAZO 33); 2,2′-azobis(2-amidinopropane)dihydrochloride (available under the trade designation VAZO 50);2,2′-azobis(2,4-dimethylvaleronitrile) (available under the tradedesignation VAZO 52); 2,2′-azobis(isobutyronitrile) (also known as AIBN,available under the trade designation VAZO 64);2,2′-azobis-2-methylbutyronitrile (available under the trade designationVAZO 67); 1,1′-azobis(1-cyclohexanecarbonitrile) (available under thetrade designation VAZO 88), all of which are available from E.I. Dupontde Nemours and Company, Wilmington, Del., and2,2′-azobis(methylisobutyrate) (available under the trade designationV-601 from Wako Pure Chemical Industries, Ltd., Osaka, Japan), and otherazo compounds.

[0206] In one embodiment, the free radical initiator is aninhibitor-containing peroxide, such as 2,6-di-tert-butylbenzoquinone,2,6-di-tert-butyl-4-methylene-2,5-cyclohexadiene-1-one,2,6-di-tert-butyl-4-hydroxybenzaldehyde,2,6-di-tert-butyl-4-isopropylphenol, 4,4′-methylenebis-(2,6-di-tert-butylphenol),1,2-bis-(3,5-di-tert-butyl-4-hydroxyphenyl)ethane,2,3,5,6-tetramethylbenzoquinone, 2-tert-butylhydroquinone,2,2′-methylenebis-(4-methyl-6-tert-butylphenol), and the like, andmixtures thereof. The initiator, i.e., photoinitiator, free-radicalinitiator or cationic initiator, is generally present in an amountsufficient to initiate a polymerization resulting in a polymer having anumber average molecular weight suitable for use in golf balls, which istypically from about 1,000 to about 10,000,000 grams/mole.Alternatively, the initiator (i.e., photoinitiator, free radicalinitiator or cationic initiator) may be present in an amount greaterthan about 0.01 parts per hundred of the polymer component, preferablyfrom about 0.01 to about 15 parts per hundred of the polymer component,and more preferably from about 0.1 to about 10 parts per hundred of thepolymer component, and most preferably from about 0.2 to about 5 partsper hundred of the total polymer component. It should be furtherunderstood that heat often facilitates initiation of the generation offree radicals in the aforementioned compounds.

[0207] In another embodiment, the initiator is selected to suit or matchthe radiation cure technique that is used to initiate the polymerizationprocess. For example, a photoinitiator is used when ultraviolet (“UV”)curing is the radiation cure technique. In another example, a thermalfree radical initiator is used when thermal or heat curing is theradiation cure technique. It is possible to use a photoinitiator inthermal or heat curing, or a thermal free radical initiator in UVcuring. Thus, the present invention encompasses the use of any initiatorin conjunction with any radiation cure technique so long as theinitiator that is chosen initiates the polymerization process.

[0208] In one embodiment, the free-radical source may alternatively oradditionally be one or more of an electron beam, visible light, UV orgamma radiation, x-rays, or any other high-energy radiation sourcecapable of generating free radicals. Thus in one example, an initiatormay or may not be utilized when gamma radiation, x-ray, or electron beamradiation is the radiation cure technique. Such initiators form freeradicals and/or cations that initiate polymerization upon exposure togamma radiation, x-ray or electron beam radiation.

[0209] IPN as a Coating Composition

[0210] As briefly addressed above, the IPNs of the present invention mayalso be used as a coating. The method of forming the IPN when it isintended to be used as a coating is similar to that described above,however, the mixture of components is prepared in a solution with asolvent such as methyl isobutyl ketone, toluene, and the like. Thesolvent may be used in an amount of about 0.05 to about 4 pounds solventper pound of resin. In one embodiment, the solvent to resin ratio isabout 0.08 to about 3 by pound weight. In another embodiment, thesolvent to resin ratio is about 1 pound to about 2.5 by pound weight.The ratio of the first polymeric system, i.e., the polyurethane orpolyurea prepolymer, to the second polymeric system, i.e., the epoxyresin or acrylate resin, is preferably about 0.1 to about 1.0 by weight.In one embodiment, the ratio of the prepolymer to epoxy resin oracrylate resin is about 0.2 to about 0.8 by weight. In anotherembodiment, the prepolymer to epoxy or acrylate resin ratio is about 0.3to about 0.7 by weight.

[0211] The solution is applied to the surface of the golf equipment,e.g., an outermost cover of a golf ball, a golf club head, a golf shoe,a golf bag, by any suitable method. For example, dipping, spraying, andbrushing are application methods contemplated by the present invention.Once applied, the solution is cured in a manner similar to the onediscussed above. For example, the coated surface may be exposed to anelevated temperature to deblock the isocyanate groups in thepolyurethane or polyurea prepolymer. The elevated temperature will alsoactivate the epoxy or acrylate resin reaction so that the second systemwill cure simultaneously with the polyurethane or polyurea system toform the IPN of the present invention. As mentioned above, thetemperature required for deblocking the isocyanate groups and initiatingthe epoxy or acrylate resin reaction is a function of the type ofblocking agent, the type and amount of curing agents/catalyzingagents/initiators, as well as other factors known to those of skill inthe art.

[0212] Furthermore, as discussed above, a catalyst may be added to thesolution before it is applied to decrease the temperature and/or timerequired to deblock the isocyanate groups.

[0213] As those of ordinary skill in the art are aware, the cure time ishighly dependent on the temperature and constituents of the composition.For example, the cure time for an IPN coating composition of the presentinvention can be from about 5 seconds to 24 hours, from about 5 secondsto about 1 hour, from about 5 seconds to about 30 minutes, from about 5seconds to about 15 minutes, from about 5 seconds to about 5 minutes,from about 5 seconds to about 2 minutes, or from about 5 seconds toabout 30 seconds.

[0214] Additives

[0215] Other compounds useful in polymerization of the individualpolymeric systems of the IPNs of the present invention may also be addedto a precursor package as the situation warrants providing that thecompounds are not significantly counterproductive toward polymerizationor network formation of other components in the IPNs of the presentinvention. Such compounds should generally be chosen based on thespecifics of the starting materials, polymerization scheme, andcrosslinking reaction used to synthesize each polymer component ornetwork.

[0216] For example, accelerators or catalysts may be included in aprecursor package to control the speed and/or duration of polymerizationand/or crosslinking reaction(s), if a particular component iscrosslinked. Any accelerator or catalyst known to one of ordinary skillin the art or any standard accelerator or catalyst may be used in aprecursor package in the present invention. It should be understood,however, that the accelerator or catalyst used in a given precursorpackage should be chosen based on the specifics of the startingmaterials, polymerization scheme, and crosslinking reaction, used tosynthesize each polymer component or network. For example, the catalystmay be the same or different from the catalyst used to decrease thetemperature required to deblock the isocyanate groups in the firstpolymeric system.

[0217] Suitable catalysts include, but are not limited to, Lewis acids,for example, such as halides of boron, aluminum, indium, tin, antimony,any transition metal, particularly vanadium, zinc, zirconium, indium,manganese, molybdenum, cobalt, titanium, or tungsten, or mixturesthereof. Exemplary catalysts include chlorides and fluorides of boron,aluminum, or titanium, or mixtures thereof, and more preferably includeboron trifluoride, aluminum trichloride, titanium (III) or (IV)chloride, or mixtures thereof. Other suitable catalysts include, but arenot limited to, Lewis bases, inorganic bases, primary and secondaryamines, and amides. Other catalysts include, but are not limited to,oxides, such as magnesium oxide, or aluminum oxide; tertiary amines,such as N,N-dimethylaminopyridine, or benzyldimethylamine; imidazoles,such as 2-ethyl-4-methylimidazole; and phosphines, such astriphenylphosphine, or tributylphosphine. Catalysts may also includemixtures of any of these listed compounds with one or more othercomponents.

[0218] Suitable accelerators include, but are not limited to,sulfonamides, such as benzenesulfonamide; ureas, such as3-(p-chlorophenyl)-1,1-dimethylurea, or3-(3,4-dichlorophenyl)-1,1-dimethylurea; and acids, such as phthalicacid, benzoic acid, or p-toluenesulfonic acid. In one embodiment, acarboxylic acid compound may be used as an accelerator, particularlywhen the first polymeric system is polyurethane-based.

[0219] Optionally, additional curing agents may also be added to aprecursor package to facilitate the curing of a particular polymericsystem. Suitable chain extenders may vary depending on the polymers ornetworks included in the IPN, but, for step-growth or condensationpolymers or epoxies, suitable curing agents generally include polyols,including, for example, telechelic diols, telechelic alkanediols, suchas ethylene glycol, 1,4-butanediol, 1,6-hexanediol, and the like, ormixtures thereof; a polyamine, including, for example, telechelicdiamines, telechelic alkanediamines, such as ethylenediamine,propylenediamine, and the like, or mixtures thereof; a cyclic polyol orpolyamine, for example, such as diaminocyclohexane; or mixtures thereof.Suitable crosslinkers may also vary depending or networks included inthe IPN, and include, but are not limited to any chain extender; adisulfide or polysulfide; a diisocyanate or polyisocyanate; excessdiisocyanate or polyisocyanate; compounds containing or able to generateor activate a free radical; a form of energy able to generate oractivate a free-radical, for example, such as heat, visible light,ultraviolet light, x-rays, γ-rays, other energy or radiation, or amixture thereof; divalent or multivalent salts; or a mixture thereof.

[0220] Other curing agents may be reactive upon addition to a precursorpackage or to a polymer component or may require activation of some sortto begin curing. Certain IPN precursors, prepolymers, or polymers, whenthe proper activators or initiators are used, as understood by those ofordinary skill in the art, can undergo self-polymerization, to formhigher molecular weight polymers, or self-crosslinking, to form anetwork structure, or both. These self-reactions advantageously may befacilitated by one or more catalysts.

[0221] Certain curing agents may already be present in a precursorpackage as they may derive from a functional group or active site on apolymer component. Other curing agents may also be comonomers, forexample, such as multifunctional compounds in step-growth polymerizationreactions, such as polyamines, polyisocyanates, polyols, or the like, ormixtures thereof, or compounds containing two sites across which anaddition polymerization may proceed, such as conjugated dienes,non-conjugated dienes, divinyl compounds, conjugated or non-conjugatedcyclic compounds, divalent or multivalent salts, or mixtures thereof.One of ordinary skill in the art should be able to determine for aparticular IPN system whether certain curing agents function as chainextenders, crosslinkers, or both. It should be understood that anycuring agents already present in a precursor package or useful inanother capacity in the polymer component of the IPN system shall not beconsidered additional curing agents for that polymer component.

[0222] Fillers may also be used in the IPNs of the present invention.Fillers typically include processing aids or compounds to affectrheological and mixing properties, the specific gravity (i.e.,density-modifying fillers), the modulus, the tear strength,reinforcement, and the like. A density adjusting filler may be used tocontrol the moment of inertia, and thus the initial spin rate of theball and spin decay. Fillers are typically polymeric or inorganic innature, and, when used, are typically present in an amount from about0.1 to 50 weight percent of the layer in which they are included. Anysuitable filler available to one of ordinary skill in the art may beused. Exemplary fillers include, but are not limited to, precipitatedhydrated silica; clay; talc; glass fibers; aramid fibers; mica; calciummetasilicate; barium sulfate; zinc sulfide; lithopone; silicates;silicon carbide; diatomaceous earth; polyvinyl chloride; carbonates suchas calcium carbonate and magnesium carbonate; metals such as titanium,tungsten, aluminum, bismuth, nickel, molybdenum, iron, copper, boron,cobalt, beryllium, zinc, and tin; metal alloys such as steel, brass,bronze, boron carbide whiskers, and tungsten carbide whiskers; metaloxides such as zinc oxide, iron oxide, aluminum oxide, titanium oxide,magnesium oxide, and zirconium oxide; particulate carbonaceous materialssuch as graphite, carbon black, cotton flock, natural bitumen, celluloseflock, and leather fiber; micro balloons such as glass and ceramic; flyash; cured, ground rubber; or combinations thereof.

[0223] Various foaming agents or blowing agents may also be used in theIPNs of the present invention. Foamed polymer blends may be formed byblending ceramic or glass microspheres with polymer material. Polymeric,ceramic, metal, and glass microspheres may be solid or hollow, andfilled or unfilled.

[0224] Additional materials conventionally included in golf ballcompositions may also be included in the IPNs of the present invention.These additional materials include, but are not limited to, coloringagents, reaction enhancers, whitening agents, UV absorbers, hinderedamine light stabilizers, defoaming agents, processing aids, and otherconventional additives. Stabilizers, softening agents, plasticizers,including internal and external plasticizers, impact modifiers, foamingagents, excipients, reinforcing materials and compatibilizers can alsobe added to any composition of the invention. All of these materials,which are well known in the art, are added for their usual purpose intypical amounts.

[0225] IPN Properties

[0226] Compatibility of the IPNs of the present invention can beevidenced by comparing experimentally measured properties, such as therelative glass transition temperatures (or the difference between them,denoted as ΔT_(g)) or the relative crystallinity or crystallineperfection (as represented by the area under the melting endotherm), ifat least one component of the IPN is crystallizable. These propertiesmay be experimentally observed by a number of different instruments,such as a differential scanning calorimeter (“DSC”) or dynamicmechanical analyzer (“DMA”) or dynamic mechanical thermal analyzer(“DMTA”).

[0227] Preferably, the formation of an IPN reduces the ΔT_(g) between atleast two of the polymeric components of the IPN at least about 5percent as compared with the ΔT_(g) between a polymer blend containingthe same two polymeric components. In one embodiment, the formation ofan IPN reduces the ΔT_(g) between at least two of the polymericcomponents of the IPN at least about 10 percent over that of a polymerblend containing the same two polymeric components. In anotherembodiment, the formation of an IPN reduces the ΔT_(g) between at leasttwo of the polymeric components of the IPN at least about 20 percent ascompared to a polymer blend including the same two polymeric components.In yet another embodiment, the formation of an IPN reduces the ΔT_(g)between at least two of the polymeric components by at least about 35percent, preferably by at least about 50 percent, and more preferably byat least about 75 percent as compared with a polymer blend including thesame two polymeric components. In yet another embodiment, the formationof an IPN yields only one observable T_(g) for the at least twopolymeric components.

[0228] Alternately, in the case where at least two of the polymericcomponents of the IPN associate or interact strongly in a polymer blend,especially through hydrogen-bonding, ionic aggregation, chelation, orthe like, the formation of an IPN can increase the ΔT_(g) between the atleast two polymeric components in the IPN, in some cases at least about5 percent, as compared with the ΔT_(g) between a polymer blendcontaining the same at least two polymeric components. In one suchalternate embodiment, the formation of an IPN increases the ΔT_(g)between at least two of the polymeric components of the IPN at leastabout 10 percent. In another such alternate embodiment, the formation ofan IPN increases the ΔT_(g) between at least two of the polymericcomponents of the IPN at least about 20 percent.

[0229] Preferably, the formation of an IPN reduces the absolute value ofthe area under the melting endotherm, often called ΔH_(f), of at leastone of the crystallizable polymeric components of the IPN at least about5 percent less than the area under the melting endotherm of a polymerblend of the same ratio of the at least one crystallizable polymericcomponent. In one embodiment, the formation of an IPN reduces ΔH_(f) ofat least one of the crystallizable polymeric components of the IPN atleast about 10 percent compared to the blend. In another embodiment, theformation of an IPN reduces ΔH_(f) of at least one of the crystallizablepolymeric components of the IPN at least about 15 percent compared tothe blend. In various other embodiments, the formation of an IPN reducesΔH_(f) of at least one of the crystallizable polymeric components of theIPN at least about 25 percent compared to the blend, at least about 50percent compared to the blend, and at least about 75 percent compared tothe blend. In yet another embodiment, the formation of an IPN results inat least one of the crystallizable polymeric components beingsubstantially free of crystallinity, as measured by ΔH_(f).

[0230] When performing DMA or DMTA experiments, ASTM D4065-95 wasfollowed in analyzing sample material responses. A heating rate of nomore than about 2° C./min was employed for these tests, and thethicknesses of the samples were kept within about 5 percent of theaverage thickness. When performing DSC experiments to measure the glasstransition temperature, T_(g), or the melting temperature, T_(pm), ofsamples, ASTM D3418-99 was followed, in which the numerical value ofT_(g) represents the median temperature of the transition and thenumerical value of T_(pm) represents the peak extremum of the meltingendotherm. When performing DSC experiments to measure the degree ofcrystallinity or the area under the melting endotherm, ΔH_(f), ASTMD3417-99 was followed.

[0231] As is very often the case in multi-polymer blend systems, two ofthe polymeric components may be immiscible or partially miscible, suchthat phase separation occurs to a certain extent. This phase separationmay be visible to one of ordinary skill in the art (macrophaseseparation) or may only be observable through specializedcharacterization techniques designed to probe regions of less than about500 microns (microphase separation). At the meeting of the at least twophases, there is a phase boundary that defines the edge of each phase.The average size of the phases of each phase separated component can beexperimentally measured using, for example, atomic force microscopy,scanning electron microscopy, transmission electron microscopy, or otherappropriate characterization apparatus.

[0232] In a preferred embodiment, the formation of an IPN, in which twoof the polymeric components may be immiscible or partially miscible,results in an average phase size of each phase separated component thatcan be considerably less than the average phase size of each phaseseparated component in a blend of two or more of the components. In oneembodiment, the formation of an IPN results in an average phase size ofeach phase separated component being at least about 10 percent smallerthan a blend of the two components. In another embodiment, the formationof an IPN results in an average phase size of each phase separatedcomponent being at least about 20 percent smaller than a blend of thetwo components. In various other embodiments, the formation of an IPNresults in an average phase size of each phase separated component beingat least about 35 percent smaller than a blend of the two components, atleast about 60 percent smaller than a blend of the two components, andat least about 85 percent smaller than a blend of the two components. Insome cases, IPN formation can result in complete miscibility of thesystem, resulting in no discernible phase boundaries, while thecomponents may have been immiscible or only partially miscible when in ablend.

[0233] In one embodiment, the formation of an IPN increases at least oneof the following measurable quantities: the area under the loss moduluspeak, represented by a local maximum in E″, or loss tangent peak,represented by a local maximum in tan δ; the temperature range overwhich the loss modulus or loss tangent peak extends; the full-width athalf-maximum height (FWHM) of the loss modulus or loss tangent peak; orthe number of loss modulus or loss tangent peaks over a giventemperature interval, as compared to the same value(s) measured for ablend of the same ratio of the at least two IPN components. In anotherembodiment, the formation of an IPN increases at least one of theaforementioned measurable quantities by at least about 2 percent, ascompared to the same value(s) measured for a blend of the same ratio ofthe at least two IPN components. In yet another embodiment, theformation of an IPN increases at least one of the aforementionedmeasurable quantities by at least about 5 percent, as compared to thesame value(s) measured for a blend of the same ratio of the at least twoIPN components. In still another embodiment, the formation of an IPNincreases at least one of the aforementioned measurable quantities by atleast about 10 percent, as compared to the same value(s) measured for ablend of the same ratio of the at least two IPN components. In variousother embodiments, the formation of an IPN increases at least one of theaforementioned measurable quantities by at least about 25 percent, by atleast about 50 percent, and by at least about 75 percent, as compared tothe same value(s) measured for a blend of the same ratio of the at leasttwo IPN components. Alternately, instead of a comparison to the value(s)measured for a blend of the same ratio of the at least two IPNcomponents, at least one of the aforementioned measure quantities can becompared to an uncrosslinked polymer of one of the at least two IPNcomponents, a crosslinked polymer of one of the at least two IPNcomponents, a random, block, graft, or other type of copolymer of atleast two of the individual polymer components of the IPN, a crosslinkedcopolymer of at least two of the individual polymer components of theIPN, or some combination thereof.

[0234] It is also desirable for the cover, or the outermost layer of thecover if the cover has a plurality of layers, to exhibit a high shearresistance, which is manifest as the ability of a material to maintainits mechanical stability and integrity upon the application of a shearstress to that material. A “shear resistance rating” is a qualitative,or relative, scale for assessing the relative shear resistance of amaterial. The lower the shear resistance rating is, the higher the shearresistance of the material. For painted golf ball cover materials, theshear resistance rating categories from 1 to 5 are listed and describedin the table below: Description Rating No visible damage to cover orpaint 1 Paint damage only 2 Slight cover shear and/or paint damageobserved 3 Moderate cover shear; fraying; and/or slight material removed4 Extensive cover shear; heavy material removed; and/or severe 5material clumping

[0235] The shear resistance rating can be determined by using a Miya™mechanical Golf Swing Machine, commercially available from Miyamae Co.,Ltd., of Osaka, Japan, to make two hits on each of about 6 to 12substantially identical golf balls of substantially the same compositionwith either a sand wedge or a pitching wedge. First, the test conditionsare adjusted and verified so that a control golf ball having a balatacover produces a rating of 5 on the shear resistance rating scale above.Following the calibration procedure, each experimental golf ball istested and assigned a rating based upon visible manifestations of damageafter being struck. The shear resistance rating for a golf ball coverlayer of a given composition represents a numerical average of all thetested substantially identical golf balls. One alternative way to testshear resistance of a golf ball cover involves using player-testing andevaluating the results after the ball is struck multiple times withwedges and/or short irons.

[0236] In a preferred embodiment, the formation of an IPN in a layer ofa golf ball according to the present invention increases the shearresistance of the cover layer of that golf ball, preferably resulting ina decrease in the shear test rating of at least 1, more preferablyresulting in a decrease of at least 2, compared to the cover layermaterial of a conventional golf ball that is substantially free of IPNand that is made of the same components as the IPN. In that embodiment,it is preferred that the shear resistance of the cover layer of thatgolf ball has a shear test rating of 3 or less, most preferably 2 orless.

[0237] Advantageously, the formation of an IPN in a golf ball layer mayalso increase the resistance to moisture penetration of that layer. IPNformation in that layer may also provide reduction in the water vaporpermeability of a golf ball layer having an IPN therein. The reducedexposure of golf ball materials to water or water vapor helps inhibitdegradation of or maintain the mechanical and/or chemical properties ofthose materials. This is particularly true when the water or moisturecan facilitate degradation of molecular weight or mechanical propertiesof one or more components of the materials within the golf ball.

[0238] The ranges of values of several golf ball or material propertieslisted herein can vary, even outside their recited ranges, by theinclusion of IPNs according to the invention and, if necessary, byselectively varying at least one other property mentioned herein.Examples of such golf ball or material properties whose ranges can bevaried by inclusion of an IPN include, but are not limited to, tensileor flexural modulus and impact resistance.

[0239] Golf Ball Construction

[0240] The compositions of the present invention may be used with anytype of ball construction including, but not limited to, one-piece,two-piece, three-piece, and four-piece designs, a double core, a doublecover, an intermediate layer(s), a multilayer core, and/or a multi-layercover depending on the type of performance desired of the ball. That is,the compositions of the invention may be used in a core, an intermediatelayer, and/or a cover of a golf ball, each of which may have a singlelayer or multiple layers. As used herein, the term “multilayer” means atleast two layers.

[0241] For instance, the core may be a one-piece core or a multilayercore, both of which may be solid, semi-solid, hollow, fluid-filled, orpowder-filled. As used herein, the term “fluid” includes a liquid, apaste, a gel, a gas, or any combination thereof A “fluid-filled” golfball center or core according to the invention also includes a hollowcenter or core. A multilayer core is one that has an innermost componentwith an additional core layer or additional core layers disposedthereon. In addition, when the golf ball of the present inventionincludes an intermediate layer, this layer may be incorporated with asingle or multilayer cover, a single or multi-piece core, with both asingle layer cover and core, or with both a multilayer cover and amultilayer core. The intermediate layer may be an inner cover layer orouter core layer, or any other layer(s) disposed between the inner coreand the outer cover of a golf ball. As with the core, the intermediatelayer, if included, and the cover layer may include a plurality oflayers. It will be appreciated that any number or type of intermediateand cover layers may be used, as desired. For example, the intermediatelayer may also be a tensioned elastomeric material wound around a solid,semi-solid, hollow, fluid-filled, or powder-filled center.

[0242] Referring to FIG. 1, a golf ball 10 of the present invention caninclude a center 12 and a cover 16 surrounding the center 12. Referringto FIG. 2, a golf ball 20 of the present invention can include a center22, a cover 26, and at least one intermediate layer 24 disposed betweenthe cover and the center. In one embodiment, the intermediate layer 24is disposed within the core, which also includes a center 22 and mayoptionally include a wound layer (not shown). In another embodiment, theintermediate layer 24 is disposed outside of the core, which mayoptionally include a wound layer (not shown), but which is disposedunder the cover layer 26. Each of the cover and center layers in FIG. 1or 2 may include more than one layer, i.e., the golf ball can be aconventional three-piece wound ball, a two-piece ball, a ball having amulti-layer core and an intermediate layer or layers, etc. Also, FIG. 3shows a golf ball 30 of the present invention including a center 32, acover 38, and an intermediate layer 34 located within the core 33.

[0243] Alternately, also referring to FIG. 3, a golf ball 30 of thepresent invention can include a center 32, a cover 38, and anintermediate layer 36 disposed between the cover and the core 33.Although FIG. 3 shows golf balls with only one intermediate layer, itwill be appreciated that any number or type of intermediate layers maybe used whether inside or outside the core, or both, as desired.Further, any of the figures detailed herein may include embodimentswherein an optional wound layer is disposed between the center and thecore of the golf ball.

[0244] Other non-limiting examples of suitable types of ballconstructions that may be used with the present invention include thosedescribed in U.S. Pat. Nos. 6,056,842, 5,688,191, 5,713,801, 5,803,831,5,885,172, 5,919,100, 5,965,669, 5,981,654, 5,981,658, and 6,149,535, aswell as in Publication Nos. US2001/0009310 A1, US2002/0025862, andUS2002/0028885. The entire disclosures of these patents and publishedpatent applications are incorporated by reference herein.

[0245] Layer Compositions

[0246] GolfBall Core Layer(s) The cores of the golf balls formedaccording to the invention may be solid, semi-solid, hollow,fluid-filled or powder-filled, one-piece or multi-component cores. Asused herein, the terms core and center are generally usedinterchangeably to reference the innermost component of the ball. Insome embodiments, however, the term “center” is used when there aremultiple core layers, i.e., a center and an outer core layer. The term“semi-solid” as used herein refers to a paste, a gel, or the like.

[0247] Any core material known to one of ordinary skill in that art issuitable for use in the golf balls of the invention. Suitable corematerials include thermoset materials, such as rubber, styrenebutadiene, polybutadiene, isoprene, polyisoprene, trans-isoprene, aswell as thermoplastics such as ionomer resins, polyamides or polyesters,and thermoplastic and thermoset polyurethane elastomers. For example,butadiene rubber, which, in an uncured state, typically has a Mooneyviscosity greater than about 20, preferably greater than about 30, andmore preferably greater than about 40, may be used in one or more corelayers of the golf balls prepared according to the present invention.Mooney viscosity is typically measured according to ASTM D1646-99. Inaddition, the IPNs of the present invention may also be incorporatedinto any component of a golf ball, including the core.

[0248] A free-radical source, often alternatively referred to as afree-radical initiator, may optionally be used in the core, or one ormore layers of the golf balls according to the invention, particularlywhen a polymer component includes a thermoset material. The free-radicalsource for non-IPN components may be similar to that used in an IPN ofthe present invention or may be selected from the same or other suitablecompounds.

[0249] The free radical source for non-IPN components is preferably aperoxide, more preferably an organic peroxide. The peroxide is typicallypresent in an amount greater than about 0.1 parts per hundred of thetotal polymer component, preferably about 0.1 to 15 parts per hundred ofthe polymer component, and more preferably about 0.2 to 5 parts perhundred of the total polymer component. It should be understood by thoseof ordinary skill in the art that the presence of certain components mayrequire a larger amount of free-radical source than the amountsdescribed herein. The free radical source may alternatively oradditionally be one or more of an electron beam, UV or gamma radiation,x-rays, or any other high energy radiation source capable of generatingfree radicals. It should be further understood that heat oftenfacilitates initiation of the generation of free radicals when peroxidesare used as a free-radical initiator.

[0250] GolfBall Intermediate Layer(s)

[0251] When the golf ball of the present invention includes anintermediate layer, such as an inner cover layer or outer core layer,i.e., any layer(s) disposed between the inner core and the outer coverof a golf ball, this layer can include any materials known to those ofordinary skill in the art including thermoplastic and thermosettingmaterials. In one embodiment, the intermediate layer is formed, at leastin part, from an IPN of the invention.

[0252] The intermediate layer(s) may also be formed, at least in part,from one or more homopolymeric or copolymeric materials, such asionomers, primarily or fully non-ionomeric thermoplastic materials,vinyl resins, polyolefins, polyurethanes, polyureas, such as thosedisclosed in U.S. Pat. No. 5,484,870, polyamides, acrylic resins andblends thereof, olefinic thermoplastic rubbers, block copolymers ofstyrene and butadiene, isoprene or ethylene-butylene rubber,copoly(ether-amide), such as PEBAX, sold by Atofina Chemicals, Inc. ofPhiladelphia, Pa., polyphenylene oxide resins or blends thereof, andthermoplastic polyesters.

[0253] For example, the intermediate layer may be formed of low acidionomers, such as those described in U.S. Pat. Nos. 6,506,130 and6,503,156, high acid ionomers, highly neutralized polymers, such asthose disclosed in U.S. Patent Publication Nos. 2001/0018375 and2001/0019971, or mixtures thereof. The intermediate layer may also beformed from the compositions as disclosed in U.S. Pat. No. 5,688,191.The entire disclosures of these patents and publications areincorporated herein by express reference thereto.

[0254] The intermediate layer may also include a wound layer formed froma tensioned thread material. Many different kinds of thread materialsmay be used for the wound layer of the present invention. The thread maybe single-ply or may include two or more plies. Preferably, the threadof the present invention is single-ply. The thread may be selected tohave different material properties, dimensions, cross-sectional shapes,and methods of manufacturing. If two or more threads are used, they maybe identical in material and mechanical properties or they may besubstantially different from each other, either in cross-section shapeor size, composition, elongated state, and mechanical or thermalproperties. Mechanical properties that may be varied include resiliency,elastic modulus, and density. Thermal properties that may be variedinclude melt temperature, glass transition temperature and thermalexpansion coefficient.

[0255] The tensioned thread material of the wound layer may encompassany suitable material, but typically includes fiber, glass, carbon,polyether urea, polyether block copolymers, polyester urea, polyesterblock copolymers, syndiotactic- or isotactic-poly(propylene),polyethylene, polyamide, poly(oxymethylene), polyketone, poly(ethyleneterephthalate), poly(p-phenylene terephthalamide), poly(acrylonitrile),diaminodicyclohexylmethane, dodecanedicarboxylic acid, natural rubber,polyisoprene rubber, styrene-butadiene copolymers,styrene-propylene-diene copolymers, another synthetic rubber, or block,graft, random, alternating, brush, multi-arm star, branched, ordendritic copolymers, or mixtures thereof.

[0256] Threads used in the present invention may be formed using avariety of processes including conventional calendering and slitting,melt spinning, wet spinning, dry spinning and polymerization spinning.Any process available to one of ordinary skill in the art may beemployed to produce thread materials for use in the wound layer. Thetension used in winding the thread material of the wound layer may beselected as desired to provide beneficial playing characteristics to thefinal golf ball. The winding tension and elongation may be kept the sameor may be varied throughout the layer. Preferably, the winding occurs ata consistent level of tension so that the wound layer has consistenttension throughout the layer.

[0257] In addition, the winding patterns used for the wound layer can bevaried in any way available to those of ordinary skill in the art.Although one or more threads may be combined to begin forming the woundlayer, it is preferred to use only a single continuous thread.

[0258] Golf Ball Cover(s)

[0259] The cover provides the interface between the ball and a club.Properties that are desirable for the cover are good moldability, highabrasion resistance, high impact resistance, high tear strength, highresilience, and good mold release, among others. The cover layer may beformed, at least in part, from an IPN of the invention.

[0260] When an IPN of the invention is incorporated into a core orintermediate/inner cover layer, the cover compositions may include oneor more homopolymeric or copolymeric materials as discussed in thesection above pertaining to the intermediate layer. The cover may alsobe at least partially formed from the polybutadiene reaction productdiscussed above with respect to the core.

[0261] As discussed elsewhere herein, the cover may be molded onto thegolf ball in any known manner, such as by casting, compression molding,injection molding, reaction injection molding, or the like. One skilledin the art would appreciate that the molding method used may bedetermined at least partially by the properties of the composition. Forexample, casting may be preferred when the material is thermoset,whereas compression molding or injection molding may be preferred forthermoplastic compositions.

[0262] The golf balls of the present invention can likewise include oneor more homopolymeric or copolymeric thermoplastic or thermosetmaterials in a center, an intermediate layer, and/or a cover, eitherindividually or in combination with any other available materials or ina blend with any IPN according to the invention. In one embodiment, theone or more portions of the ball including IPN material will not includeblends with conventional materials. One of ordinary skill in the artwould know that most of the polymeric materials listed below may belongin the thermoplastic category or in the thermoset category, dependingupon the nature of the repeat units, functional groups pendant from therepeat units, method of polymerization, method of formation, temperatureof formation, post-polymerization treatments, and/or many other possiblefactors, and are suitable for use in golf balls according to theinvention. The materials include, but are not limited to, the followingpolymers, or their set of monomeric, oligomeric, or macromonomericprecursors:

[0263] (1) Vinyl resins, for example, such as those formed by thepolymerization of vinyl chloride, or by the copolymerization of vinylchloride with vinyl acetate, acrylic esters or vinylidene chloride;

[0264] (2) Polyolefins, for example, such as polyethylene,polypropylene, polybutylene, and copolymers, such as ethylenemethylacrylate, ethylene ethylacrylate, ethylene vinyl acetate, ethylenemethacrylic acid, ethylene acrylic acid, or propylene acrylic acid, aswell as copolymers and homopolymers, such as those produced using asingle-site catalyst or a metallocene catalyst;

[0265] (3) Polyurethanes, for example, such as those prepared fromdiols, triols, or polyols and diisocyanates, triisocyanates, orpolyisocyanates, as well as those disclosed in U.S. Pat. No. 5,334,673;

[0266] (4) Polyureas, for example, such as those prepared from diamines,triamines, or polyamines and diisocyanates, triisocyanates, orpolyisocyanates, as well as those disclosed in U.S. Pat. No. 5,484,870;

[0267] (5) Polyamides, for example, such as poly(hexamethyleneadipamide) and others prepared from diamines and dibasic acids, as wellas those from amino acids such as poly(caprolactam), and blends ofpolyamides with SURLYN, polyethylene, ethylene copolymers,ethyl-propylene-non-conjugated diene terpolymer, and the like;

[0268] (6) Acrylic resins and blends of these resins with, for example,polymers such as poly vinyl chloride, elastomers, and the like;

[0269] (7) Olefinic rubbers, for example, such as blends of polyolefinswith ethylene-propylene-non-conjugated diene terpolymer; blockcopolymers of styrene and butadiene, isoprene or ethylene-butylenerubber; or copoly(ether-amide), such as PEBAX, sold by ELF Atochem ofPhiladelphia, Pa.;

[0270] (8) Polyphenylene oxide resins or blends of polyphenylene oxidewith high impact polystyrene, for example, as sold under the trademarkNORYL by General Electric Company of Pittsfield, Mass.;

[0271] (9) Polyesters, for example, such as polyethylene terephthalate,polybutylene terephthalate, polyethylene terephthalate/glycol modifiedand elastomers, such as sold under the trademarks HYTREL by E.I. DuPontde Nemours & Co. of Wilmington, Del., and LOMOD by General ElectricCompany of Pittsfield, Mass.;

[0272] (10) Blends and alloys, for example including polycarbonate withacrylonitrile butadiene styrene, polybutylene terephthalate,polyethylene terephthalate, styrene maleic anhydride, polyethylene,elastomers, and the like, and polyvinyl chloride with acrylonitrilebutadiene styrene, ethylene vinyl acetate, or other elastomers;

[0273] (11) Blends of vulcanized, unvulcanized, or non-vulcanizablerubbers with polyethylene, propylene, polyacetal, nylon, polyesters,cellulose esters, and the like; and

[0274] (12) Polymers or copolymers possessing epoxy-containing, orpost-polymerization epoxy-functionalized, repeat units, for example, incombination with anhydride, ester, amide, amine, imide, carbonate,ether, urethane, urea, α-olefin, conjugated, or acid (optionally totallyor partially neutralized with inorganic salts), such as HPF-1000 andBPF-2000 commercially available from DuPont, comonomers, or copolymersor blends thereof.

[0275] Layer Formation

[0276] The golf balls of the invention may be formed using a variety ofapplication techniques such as compression molding, flip molding,injection molding, retractable pin injection molding, reaction injectionmolding (RIM), liquid injection molding (LIM), casting, vacuum forming,powder coating, flow coating, spin coating, dipping, spraying, and thelike. Conventionally, compression molding and injection molding areapplied to thermoplastic materials, whereas RIM, liquid injectionmolding, and casting are employed on thermoset materials. These andother manufacture methods are disclosed in U.S. Pat. Nos. 6,207,784 and5,484,870, the disclosures of which are incorporated herein by referencein their entirety.

[0277] The cores of the invention may be formed by any suitable methodknown to those of ordinary skill in art. When the cores are formed froma thermoset material, compression molding is a particularly suitablemethod of forming the core. In a thermoplastic core embodiment, on theother hand, the cores may be injection molded. Furthermore, U.S. Pat.Nos. 6,180,040 and 6,180,722 disclose methods of preparing dual coregolf balls. The disclosures of these patents are hereby incorporated byreference in their entirety.

[0278] The intermediate layer may also be formed from using any suitablemethod known to those of ordinary skill in the art. For example, anintermediate layer may be formed by blow molding and covered with adimpled cover layer formed by injection molding, compression molding,casting, vacuum forming, powder coating, and the like. In oneembodiment, the intermediate layer may be a moisture barrier layer asdisclosed in U.S. Pat. No. 6,632,147. Thus, a golf ball of the inventionmay include an intermediate layer that has a moisture vapor transmissionrate lower than that of the cover and, additionally, a primaryingredient of the intermediate layer is made from a material includingpolybutadiene, natural rubber, butyl-based rubber, acrylics,trans-polyisoprene, neoprene, chlorinated polyethylene, balata,multi-layer thermoplastic films, blends of ionomers, polyvinyl alcoholcopolymer and polyamides, and dispersions of acid salts ofpolyetheramines.

[0279] The IPNs of the invention may be applied over an inner ball usinga variety of application techniques such as spraying, compressionmolding, dipping, spin coating, casting, or flow coating methods thatare well known in the art. In one embodiment, the IPNs are formed overthe core using a combination of casting and compression molding. Inaddition, the IPNs may be formed around an inner ball using reactioninjection molding (RIM) and liquid injection molding (LIM) techniques.

[0280] The use of various dimple patterns and profiles provides arelatively effective way to modify the aerodynamic characteristics of agolf ball. As such, the manner in which the dimples are arranged on thesurface of the ball can be by any available method. For instance, theball may have an icosahedron-based pattern, such as described in U.S.Pat. No. 4,560,168, or an octahedral-based dimple patterns as describedin U.S. Pat. No. 4,960,281. The resultant golf balls prepared accordingto the invention typically will have dimple coverage greater than about60 percent, preferably greater than about 65 percent, and morepreferably greater than about 70 percent.

[0281] Golf Ball Post-Processing

[0282] The golf balls of the present invention may be painted, coated,or surface treated for further benefits. For example, golf balls may becoated with the IPNs of the invention in order to obtain an extremelysmooth, tack-free surface. In addition to the IPNs of the invention,other coating materials, such as urethanes, urethane hybrids, epoxies,polyesters and acrylics, may be used for coating golf balls formedaccording to the invention. If desired, more than one coating layer canbe used. The coating layer(s) may be applied by any suitable methodknown to those of ordinary skill in the art. In one embodiment, thecoating layer(s) is applied to the golf ball cover by an in-mold coatingprocess, such as described in U.S. Pat. No. 5,849,168, which isincorporated in its entirety by reference herein.

[0283] Golf Ball Properties

[0284] The properties such as core diameter, intermediate layerthickness and cover layer thickness, hardness, and compression have beenfound to effect play characteristics such as spin, initial velocity andfeel of the present golf balls.

[0285] Component Dimensions

[0286] Dimensions of golf ball components, i.e., thickness and diameter,may vary depending on the desired properties. For the purposes of theinvention, any layer thickness may be employed. For example, the presentinvention relates to golf balls of any size, although the golf ballpreferably meets USGA standards of size and weight. While “The Rules ofGolf” by the USGA dictate specifications that limit the size of acompetition golf ball to more than 1.680 inches in diameter, golf ballsof any size can be used for leisure golf play. The preferred diameter ofthe golf balls is from about 1.680 inches to about 1.800 inches. Themore preferred diameter is from about 1.680 inches to about 1.760inches. A diameter of from about 1.680 inches (43 mm) to about 1.740inches (44 mm) is most preferred, however diameters anywhere in therange of from 1.700 to about 1.950 inches can be used. Preferably, theoverall diameter of the core and all intermediate layers is about 80percent to about 98 percent of the overall diameter of the finishedball.

[0287] The core may have a diameter ranging from about 0.09 inches toabout 1.65 inches. In one embodiment, the diameter of the core of thepresent invention is about 1.2 inches to about 1.630 inches. In anotherembodiment, the diameter of the core is about 1.3 inches to about 1.6inches, preferably from about 1.39 inches to about 1.6 inches, and morepreferably from about 1.5 inches to about 1.6 inches. In yet anotherembodiment, the core has a diameter of about 1.55 inches to about 1.65inches. In one embodiment, the core diameter is about 1.59 inches orgreater. In another embodiment, the diameter of the core is about 1.64inches or less.

[0288] When the core includes an inner core layer and an outer corelayer, the inner core layer is preferably about 0.9 inches or greaterand the outer core layer preferably has a thickness of about 0.1 inchesor greater. In one embodiment, the inner core layer has a diameter fromabout 0.09 inches to about 1.2 inches and the outer core layer has athickness from about 0.1 inches to about 0.8 inches. In yet anotherembodiment, the inner core layer diameter is from about 0.095 inches toabout 1.1 inches and the outer core layer has a thickness of about 0.20inches to about 0.03 inches.

[0289] The cover typically has a thickness to provide sufficientstrength, good performance characteristics, and durability. In oneembodiment, the cover thickness is from about 0.02 inches to about 0.12inches, preferably about 0.1 inches or less. In another embodiment, thecover thickness is about 0.05 inches or less, preferably from about 0.02inches to about 0.05 inches, and more preferably about 0.02 inches andabout 0.045 inches.

[0290] The range of thicknesses for an intermediate layer of a golf ballis large because of the vast possibilities when using an intermediatelayer, i.e., as an outer core layer, an inner cover layer, a woundlayer, a moisture/vapor barrier layer. When used in a golf ball of theinvention, the intermediate layer, or inner cover layer, may have athickness about 0.3 inches or less. In one embodiment, the thickness ofthe intermediate layer is from about 0.002 inches to about 0.1 inches,preferably about 0.01 inches or greater. In another embodiment, theintermediate layer thickness is about 0.05 inches or less, morepreferably about 0.01 inches to about 0.045 inches.

[0291] Hardness

[0292] The golf ball layers containing the IPNs according to the presentinvention typically have a material hardness greater than about 15 ShoreA, preferably from about 15 Shore A to 85 Shore D. In one preferredembodiment, the material hardness of a golf ball layer including an IPNof the present invention is from about 10 to 85 Shore D. It should beunderstood, especially to one of ordinary skill in the art, that thereis a fundamental difference between “material hardness” and “hardness,as measured directly on a golf ball.” Material hardness is defined bythe procedure set forth in ASTM-D2240-00 and generally involvesmeasuring the hardness of a flat “slab” or “button” formed of thematerial of which the hardness is to be measured. Generally,ASTM-D2240-00 requires calibration of durometers, which have scalereadings from 0 to 100. However, readings below 10 or above 90 are notconsidered reliable, as noted in ASTM-D2240-00, and accordingly, all thehardness values herein are within this range.

[0293] In particular, the cores of the present invention may havevarying hardnesses depending on the particular golf ball construction.In one embodiment, the core hardness is at least about 15 Shore A,preferably about 30 Shore A, as measured on a formed sphere. In anotherembodiment, the core has a hardness of about 50 Shore A to about 90Shore D. In yet another embodiment, the hardness of the core is about 80Shore D or less. Preferably, the core has a hardness about 30 to about65 Shore D, and more preferably, the core has a hardness about 35 toabout 60 Shore D.

[0294] The intermediate layer(s) of the present invention may also varyin hardness depending on the specific construction of the ball. In oneembodiment, the hardness of the intermediate layer is about 30 Shore Dor greater. In another embodiment, the hardness of the intermediatelayer is about 90 Shore D or less, preferably about 80 Shore D or less,and more preferably about 70 Shore D or less. In yet another embodiment,the hardness of the intermediate layer is about 50 Shore D or greater,preferably about 55 Shore D or greater. In one embodiment, theintermediate layer hardness is from about 55 Shore D to about 65 ShoreD. The intermediate layer may also be about 65 Shore D or greater.

[0295] As with the core and intermediate layers, the cover hardness mayvary depending on the construction and desired characteristics of thegolf ball. The ratio of cover hardness to inner ball hardness is aprimary variable used to control the aerodynamics of a ball and, inparticular, the spin of a ball. In general, the harder the inner ball,the greater the driver spin and the softer the cover, the greater thedriver spin.

[0296] For example, when the intermediate layer is intended to be thehardest point in the ball, e.g., about 50 Shore D to about 75 Shore D,the cover material may have a hardness of about 20 Shore D or greater,preferably about 25 Shore D or greater, and more preferably about 30Shore D or greater, as measured on the slab. In another embodiment, thecover itself has a hardness of about 30 Shore D or greater. Inparticular, the cover may be from about 30 Shore D to about 70 Shore D.In one embodiment, the cover has a hardness of about 40 Shore D to about65 Shore D, and in another embodiment, about 40 Shore to about 55 ShoreD. In another aspect of the invention, the cover has a hardness lessthan about 45 Shore D, preferably less than about 40 Shore D, and morepreferably about 25 Shore D to about 40 Shore D. In one embodiment, thecover has a hardness from about 30 Shore D to about 40 Shore D.

[0297] Compression

[0298] Compression values are dependent on the diameter of the componentbeing measured. The Atti compression of the core, or portion of thecore, of golf balls prepared according to the invention is preferablyless than about 80, more preferably less than about 75. As used herein,the terms “Atti compression” or “compression” are defined as thedeflection of an object or material relative to the deflection of acalibrated spring, as measured with an Atti Compression Gauge, that iscommercially available from Atti Engineering Corp. of Union City, N.J.Atti compression is typically used to measure the compression of a golfball. In another embodiment, the core compression is from about 40 toabout 80, preferably from about 50 to about 70. In yet anotherembodiment, the core compression is preferably below about 50, and morepreferably below about 25.

[0299] In an alternative, low compression embodiment, the core has acompression less than about 20, more preferably less than about 10, andmost preferably, 0. As known to those of ordinary skill in the art,however, the cores generated according to the present invention may bebelow the measurement of the Atti Compression Gauge. In one embodiment,golf balls of the invention preferably have an Atti compression of about55 or greater, preferably from about 60 to about 120. In anotherembodiment, the Atti compression of the golf balls of the invention isat least about 40, preferably from about 50 to 120, and more preferablyfrom about 60 to 100. In yet another embodiment, the compression of thegolf balls of the invention is about 75 or greater and about 95 or less.For example, a preferred golf ball of the invention may have acompression from about 80 to about 95.

[0300] Coefficient of Restitution

[0301] The present invention contemplates golf balls having CORs fromabout 0.700 to about 0.850 at an inbound velocity of about 125 ft/sec.In one embodiment, the COR is about 0.750 or greater, preferably about0.780 or greater. In another embodiment, the ball has a COR of about0.800 or greater. In yet another embodiment, the COR of the balls of theinvention is about 0.800 to about 0.815.

[0302] Alternatively, the maximum COR of the ball is one that does notcause the golf ball to exceed initial velocity requirements establishedby regulating entities such as the USPGA. As used herein, the term“coefficient of restitution” (COR) is calculated by dividing the reboundvelocity of the golf ball by the incoming velocity when a golf ball isshot out of an air cannon. The COR testing is conducted over a range ofincoming velocities and determined at an inbound velocity of 125 ft/s.Another measure of this resilience is the “loss tangent,” or tan δ,which is obtained when measuring the dynamic stiffness of an object.Loss tangent and terminology relating to such dynamic properties istypically described according to ASTM D4092-90. Thus, a lower losstangent indicates a higher resiliency, thereby indicating a higherrebound capacity. Low loss tangent indicates that most of the energyimparted to a golf ball from the club is converted to dynamic energy,i.e., launch velocity and resulting longer distance. The rigidity orcompressive stiffness of a golf ball may be measured, for example, bythe dynamic stiffness. A higher dynamic stiffness indicates a highercompressive stiffness. To produce golf balls having a desirablecompressive stiffness, the dynamic stiffness of the crosslinked materialshould be less than about 50,000 N/m at −50° C. Preferably, the dynamicstiffness should be between about 10,000 and 40,000 N/m at −50° C., morepreferably, the dynamic stiffness should be between about 20,000 and30,000 N/m at −50° C.

[0303] Spin Rate

[0304] A spin rate of a golf ball refers to the speed it spins on anaxis while in flight, measured in revolutions per minute (“rpm”). Spingenerates lift, and accordingly, spin rate directly influences how highthe ball flies and how quickly it stops after landing. The golf ballsdisclosed herein can be tested to determine spin rate by initiallyestablishing test conditions using suitable control golf balls and golfclubs. For example, a spin rate of a golf ball struck by a standard golfdriver was obtained by using test conditions for a Titleist PinnacleGold golf ball that gives a ball speed of about 159 to about 161miles/hour, a launch angle of about 9.0 degrees to about 10.0 degrees,and a spin rate of about 2900 rpm to about 3100 rpm. Thus in oneembodiment, the spin rate of a golf ball hit with a golf club driverunder the same test conditions is between about 1200 rpm to about 4000rpm. In a preferred embodiment, the spin rate of a golf ball hit with agolf club driver is between about 2000 rpm to about 3500 rpm, morepreferably between about 2500 and 3000 rpm.

[0305] For an 8-iron ball spin test, a spin rate of a golf ball struckby a standard 8-iron club was obtained by using test conditions for aTitleist Pro V1 golf ball that gives a ball speed of about 114 to about116 miles/hour, a launch angle of about 18.5 to about 19.5 degrees and aspin rate of about 8100 rpm to about 8300 rpm. Thus in one embodiment,the spin rate of an average, cleanly struck 8-iron shot is between 6500rpm and 10,000 rpm. In preferred embodiment, the spin rate of anaverage, cleanly struck 8-iron shot under the same test conditions isbetween 7500 rpm and 9500 rpm, more preferably between about 8000 rpmand 9000 rpm.

[0306] Moisture Vapor Transmission

[0307] The moisture vapor transmission of a golf ball portion formedfrom the compositions of the invention may be expressed in terms ofabsorption, e.g., weight gain or size gain over a period of time at aspecific conditions, and transmission, e.g., moisture vapor transmissionrate (MVTR) according to ASTM E96-00. MVTR refers to the mass of watervapor that diffused into a material of a given thickness per unit areaper unit time at a specific temperature and humidity differential. Forexample, weight changes of a golf ball portion monitored over a periodof seven weeks in 100 percent relative humidity and 72° F. help todemonstrate which balls have better water resistance. In one embodiment,the golf ball portions of the invention have a weight gain of about 0.15grams or less after seven weeks. In another embodiment, the golf ballsof the invention have a weight gain of about 0.13 grams or less after aseven-week storage period. In still another embodiment, the weight gainof the golf balls of the invention is about 0.09 grams or less afterseven weeks. In yet another embodiment, the weight gain is about 0.06grams or less after a seven-week period. The golf balls of the inventionpreferably have a weight gain of about 0.03 grams or less over aseven-week storage period.

[0308] Size gain may also be used as an indicator of water resistance.That is, the more water a golf ball takes on, the larger a golf ballbecomes due to the water enclosed beneath the outermost layer of thegolf ball portion. Thus, the golf balls of the invention preferably haveno appreciable size gain. In one embodiment, the size gain of the golfballs of the invention after a seven-week period is about 0.001 inchesor less.

[0309] MVTR of a golf ball, or portion thereof, may be about 2 g/(m2×day) or less, such as about 0.45 to about 0.95 g/(m2× day), about 0.01to about 0.9 g/(m2× day) or less, at 38° C. and 90 percent relativehumidity.

EXAMPLES

[0310] The following examples are only representative of the methods andmaterials for use in golf ball compositions and golf balls of thisinvention, and are not to be construed as limiting the scope of theinvention in any way.

EXAMPLE 1 Golf Ball Having a Urethane-Epoxy IPN Present in the CoverLayer

[0311] The golf ball of Example 1 was prepared with a 1.585 inch (about4.03 cm) wound core around a fluid-filled center. The golf ball had afinished diameter of about 1.68 inches (about 4.27 cm). The golf ball ofExample 1 included an IPN of a polyurethane and an epoxy polymer,wherein the epoxy polymer component was about 5 percent of the IPN andthe polyurethane component was about 95 percent of the IPN. The urethaneprecursor package in Example 1 included Vibrathane B-821 prepolymer,1,4-butanediol, and T-12 dibutyltin dilaurate catalyst. The molarproportion of isocyanate groups in the Vibrathane prepolymer to hydroxylgroups in the diol was in about a 1:0.95 ratio. The epoxy precursorpackage included an epoxy resin (DER 331) and a BF₃ catalyst/curingagent to facilitate self-polymerization and self-crosslinking to form anepoxy network. In order to limit the possibility of the polyurethanebeing further chain extended with the curing agent intended for curingthe epoxy component, the epoxy curing agent was chosen to be catalyticand substantially unreactive with the polyurethane component. The epoxycuring agent chosen to prepare the ball of Example 1 was aBF₃:4-chlorobenzenamine catalyst complex. Other epoxy curing agentsinclude, but are not limited to, oxides, such as magnesium oxide, oraluminum oxide; tertiary amines, such as N,N-dimethylaminopyridine, orbenzyldimethylamine; imidazoles, such as 2-ethyl-4-methylimidazole; andphosphines, such as triphenylphosphine, or tributylphosphine.

[0312] The respective precursor packages were mixed separately until asufficient viscosity was achieved to allow mixing by hand, or from about8,000 cPs to 35,000 cPs, after which the precursor packages were mixedtogether and cast as the cover layer on wound cores to form the golfball of Example 1. The total gelation time was about 80 seconds. TABLE 1Cover/Ball Characteristics Control Example 1 Urethane component BDVibrathane/BD Vibrathane/BD precursor package (1:0.95) + 0.01 (1:0.95) +0.01 percent T-12 percent T-12 catalyst catalyst (95 percent) Epoxycomponent precursor — DER 331/10 pph BF₃ package catalyst (5 percent)Coefficient of Restitution 0.81 0.81 Corrected Compression 87 90Material Hardness 38 31 (Shore D) Cover Hardness (Shore D) 46 43 InitialVelocity (ft/sec) 255.5 255 T_(g) peak (° C., measured by −71 −67 DSC)T_(g) width (° C., measured by 17 24 DSC)

[0313] Vibrathane is an isocyanate end-capped polyurethane prepolymer,in this case VIBRATHANE B-821, which is made from MDI and a 2,000 M_(N)PTMEG polyol and is available commercially from Crompton UniroyalChemical Company, Inc., of Middlebury, Conn.; BD represents1,4-butanediol, which is available commercially from BASF of Parsippany,N.J.; T-12 represents a dibutyl tin dilaurate catalyst, which isavailable commercially from Air Products of Allentown, Pa.; DER # 331represents an epoxy resin based on a diglycidyl ether of bisphenol A(DGEBA) and is commercially available from Dow Chemical Company ofMidland, Mich.; BF₃ catalyst represents atrifluoroboron-4-chlorobenzenamine catalyst complex and is commerciallyavailable from Air Products of Allentown, Pa.

EXAMPLE 2 Golf Ball Having a Urethane-Polybutadiene Diacrylate IPNPresent in the Cover Layer

[0314] The golf ball of Example 2 includes an IPN of a polyurethane anda polybutadiene copolymer, which is prepared with a 1.585 inch (about4.03 cm) wound core around a fluid-filled center. Note that the IPN'sdisclosed in the Examples and specification herein can be used in anygolf ball construction. The golf ball has a finished diameter of about1.68 inches (about 4.27 cm). The golf ball of Example 2 includes an IPNof a polyurethane and a polybutadiene diacrylate copolymer, wherein thepolybutadiene copolymer component is about 10 percent of the IPN and thepolyurethane component is about 90 percent of the IPN. The urethaneprecursor package in Example 2 includes Vibrathane B-821 prepolymer,1,4-butanediol, and T-12 dibutyltin dilaurate catalyst. The molarproportion of isocyanate groups in the Vibrathane prepolymer to hydroxylgroups in the diol is in about a 1:0.95 ratio. The polybutadienediacrylate copolymer precursor package includes butadiene monomer or apolybutadiene resin, a diacrylate crosslinking agent, and an initiatorto facilitate crosslinking to form a polybutadiene diacrylate network.In order to limit the possibility of degradation of, or interferencewith, the polyurethane chain extension reaction, the polybutadienediacrylate copolymer crosslinking initiator preferably is chosen to besubstantially unreactive with the polyurethane. The initiator chosen toprepare the ball of Example 2 is a peroxide initiator, particularlydibenzoyl peroxide.

[0315] The respective precursor packages are mixed separately until asufficient viscosity is achieved to allow mixing by hand, or from about8,000 cPs to 35,000 cPs, after which the precursor packages are mixedtogether and cast as the cover layer on wound cores to form the golfball of Example 2.

EXAMPLE 3 Golf Ball Having a Urethane-Acrylate IPN Present in the CoverLayer

[0316] The golf ball of Example 3 is prepared with a 1.585 inch (about4.03 cm) wound core around a fluid-filled center. Again, note that theIPN's disclosed in the Examples and specification herein can be used inany golf ball construction. The golf ball has a finished diameter ofabout 1.68 inches (about 4.27 cm). The golf ball of Example 3 includesan IPN of a polyurethane and an acrylate polymer, wherein the acrylatepolymer component is about 10 percent of the IPN and the polyurethanecomponent is about 90 percent of the IPN. The urethane precursor packagein Example 3 includes Vibrathane B-821 prepolymer, 1,4-butanediol, andT-12 dibutyltin dilaurate catalyst. The molar proportion of isocyanategroups in the Vibrathane prepolymer to hydroxyl groups in the diol is inabout a 1:0.95 ratio. The acrylate precursor package includes methylmethacrylate monomer, optionally a crosslinking agent (such as adiacrylate), and an initiator to facilitate polymerization (andoptionally crosslinking) to form a methyl methacrylate polymer (andoptionally network). In order to limit the possibility of degradationof, or interference with, the polyurethane chain extension reaction, themethyl methacrylate polymerization initiator is chosen to preferably besubstantially unreactive with the polyurethane. The initiator chosen toprepare the ball of Example 3 is a free radical initiator, such asazobisisobutyronitrile (AIBN).

[0317] The respective precursor packages are mixed separately until asufficient viscosity is achieved to allow mixing by hand, or from about8,000 cPs to 35,000 cPs, after which the precursor packages are mixedtogether and cast as the cover layer on wound cores to form the golfball of Example 3.

EXAMPLE 4 Golf Ball Having a Urethane-Epoxy IPN Present in the CoverLayer

[0318] The golf ball of Example 4 is prepared with a 1.585 inch (about4.03 cm) wound core around a fluid-filled center. Yet again, note thatthe IPN's disclosed in the Examples and specification herein can be usedin any golf ball construction. The golf ball has a finished diameter ofabout 1.68 inches (about 4.27 cm). The golf ball of Example 4 includesan IPN of a polyurethane and an epoxy polymer, wherein the epoxy polymercomponent is about 10 percent of the IPN and the polyurethane componentis about 90 percent of the IPN. The urethane precursor package inExample 4 includes Vibrathane B-821 prepolymer, 1,4-butanediol, andoptionally a catalyst, such as T-12 dibutyltin dilaurate. The molarproportion of isocyanate groups in the Vibrathane prepolymer to hydroxylgroups in the diol is in about a 1:0.95 ratio. The epoxy precursorpackage includes an epoxy resin (DER 331), a BF₃ catalyst/curing agentto facilitate self-polymerization and self-crosslinking to form an epoxynetwork, and a catalyst to facilitate occasional interreactions of theurethane and the epoxy precursors or networks in the form of oxazolidonefunctional groups. In order to limit the possibility of the polyurethanebeing further chain extended with the curing agent intended for curingthe epoxy component, the epoxy curing agent is chosen to preferably becatalytic and substantially unreactive with the polyurethane component.The epoxy curing agent chosen to prepare the ball of Example 4 is aBF₃:4-chlorobenzenamine catalyst complex. The oxazolidone formationcatalyst chosen to prepare the ball of Example 4 is ethylmethylimidazole.

[0319] The respective precursor packages are mixed separately until asufficient viscosity is achieved to allow mixing by hand, or from about8,000 cPs to 35,000 cPs, after which the precursor packages are mixedtogether and cast as the cover layer on wound cores to form the golfball of Example 4.

EXAMPLE 5 Electron Beam Cure of Polyurea Prepolymer/Urea Acrylate

[0320] Various mixtures containing polyurea prepolymer/curative and ureaacrylate were cured using either electron beam radiation or thermalradiation and the DMA of resulting interpenetrating polymer networkswere analyzed and compared with respect to their crosslink density. Thecurative in the polyurea prepolymer/curative mixture is CLEARLINK 1000,which can have a polyurea prepolymer/curative mixture ratio of betweenabout 1:0.75 to about 1:1.25. The DMA results of the IPNs were obtainedusing a TA Instruments 2980 unit, using the following parameters:tensile film mode; 20 μm amplitude; 1 Hz frequency; 10 cNm clampingforce; −100 to 250° C.; 3° C./min heating rate; and 15×6.5×0.6 (mm)sampling dimensions. The sample compositions are summarized below inTable 2 and the DMA results are summarized below in Table 3. TABLE 2Amount of Polyurea Amount of Prepolymer/Clearlink Urea Acrylate SampleID 1000 (percent) (percent)  0 percent IPN 100 0 10 percent IPN 90 10 20percent IPN 80 20 30 percent IPN 70 30 40 percent IPN 60 40 100 percentIPN  0 100

[0321] TABLE 3 Relative Relative Crosslink Crosslink DMA Tg density* DMATg DMA Tg density* (° C.) (1000 moles/cc) (° C.) (° C.) (1000 moles/cc)Thermal Thermal Before Radiation Radiation Sample ID Cure Cure RadiationCure Cure  0 percent −44° C., 80° C. — −50° C., 71° C. −50° C., 73° C. —IPN 10 percent −47° C., 81° C. — −42° C., 70° C. −41° C., 74° C., — IPN120° C. 20 percent −46° C., 72° C., — −48° C. −50° C., 72° C., 0.01387IPN 135° C. 104° C. 30 percent −46° C., 72° C., 0.00358 −37° C., 43° C.−42° C., 70° C., 0.0243 IPN 131° C. 111° C. 40 percent −46° C., 66° C.,0.0124 — −42° C., 66° C. 0.058 IPN 121° C. 100 percent  −50° C., 73° C.0.83 — −42° C., 62° C. 0.5588 IPN

[0322] Other than in the operating examples, or unless otherwiseexpressly specified, all of the numerical ranges, amounts, values andpercentages such as those for amounts of materials, times andtemperatures of reaction, ratios of amounts, values for molecular weight(whether number average molecular weight (“M_(n)”) or weight averagemolecular weight (“M_(w)”), and others in the following portion of thespecification may be read as if prefaced by the word “about” even thoughthe term “about” may not expressly appear with the value, amount orrange. Accordingly, unless indicated to the contrary, the numericalparameters set forth in the following specification and attached claimsare approximations that may vary depending upon the desired propertiessought to be obtained by the present invention. At the very least, andnot as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

[0323] Notwithstanding that the numerical ranges and parameters settingforth the broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Furthermore, when numerical ranges ofvarying scope are set forth herein, it is contemplated that anycombination of these values inclusive of the recited values may be used.

[0324] The invention described and claimed herein is not to be limitedin scope by the specific embodiments herein disclosed, since theseembodiments are intended as illustrations of several aspects of theinvention. Any equivalent embodiments are intended to be within thescope of this invention. For example, although the disclosure hereinfocuses on a method of making an IPN layer for golf balls, it is alsoeasily applicable by one of ordinary skill in the art to the manufactureof other items, such as curing adhesives (e.g., in golf shoes), IPNcoatings with crosslinkable systems, and in any application thatrequires post-crosslinking of the polymer. Indeed, various modificationsof the invention in addition to those shown and described herein willbecome apparent to those skilled in the art from the foregoingdescription. Such modifications are also intended to fall within thescope of the appended claims. All patents and patent applications citedin the foregoing text are expressly incorporate herein by reference intheir entirety.

What is claimed is:
 1. A golf ball comprising at least one layer formedfrom an interpenetrating polymer network comprising: a first polymericsystem comprising a polyurethane prepolymer cured with a first curingagent, wherein the prepolymer comprises an isocyanate having terminalisocyanate groups, a blocking agent, and a polyol; and a secondpolymeric system comprising an epoxy resin and a second curing agent. 2.The golf ball of claim 1, wherein the blocking agent is selected fromthe group consisting of linear and branched alcohols; phenols and phenolderivatives; oximes; lactams; lactones; β-dicarbonyl compounds;hydroxamic acid esters; bisulfite addition compounds; hydroxylamines;esters of p-hydroxybenzoic acid; N-hydroxyphthalimide;N-hydroxysuccinimide; triazoles; substituted imidazolines;tetrahydropyrimidines; caprolactones; and mixtures thereof.
 3. The golfball of claim 2, wherein the blocking agent is selected from the groupconsisting of phenols, branched alcohols, methyl ethyl ketoxime,ε-caprolactam, ε-caprolactone, and mixtures thereof.
 4. The golf ball ofclaim 1, wherein the second curing agent is selected from the groupconsisting of anhydrides, Lewis bases, amines, amides, Lewis acids, andmixtures thereof.
 5. The golf ball of claim 1, wherein at least about 80percent of the terminal isocyanate radicals groups are blocked.
 6. Thegolf ball of claim 5, wherein at least about 95 percent or more of theterminal isocyanate groups are blocked.
 7. The golf ball of claim 1,wherein the at least one layer comprises a cover layer.
 8. The golf ballof claim 7, wherein the cover layer comprise an inner cover layer and anouter cover layer, and wherein the outer cover layer comprises theinterpenetrating polymer network.
 9. A golf ball comprising at least onelayer formed from an interpenetrating polymer network comprising: afirst polymeric system comprising a polyurethane prepolymer cured with afirst curing agent, wherein the prepolymer comprises an isocyanatehaving terminal isocyanate groups, a blocking agent, and a polyol; and asecond polymeric system comprising an acrylate resin and an initiator.10. The golf ball of claim 9, wherein the initiator comprises benzoylperoxide, t-amyl peroxide, or mixtures thereof.
 11. The golf ball ofclaim 9, wherein at least about 95 percent or more of the terminalisocyanate groups are blocked.
 12. The golf ball of claim 9, wherein atleast about 97 percent or more of the terminal isocyanate groups areblocked.
 13. The golf ball of claim 9, wherein the blocking agentcomprises linear and branched alcohols; phenols and phenol derivatives;oximes; lactams; lactones; β-dicarbonyl compounds; hydroxamic acidesters; bisulfite addition compounds; hydroxylamines; esters ofp-hydroxybenzoic acid; N-hydroxyphthalimide; N-hydroxysuccinimide;triazoles; substituted imidazolines; tetrahydropyrimidines;caprolactones; or mixtures thereof.
 14. A golf ball comprising a coreand a cover, wherein a portion of the golf ball is formed from aninterpenetrating polymer network comprising: a first polymeric systemcomprising an isocyanate having terminal isocyanate groups, a polyol,and a blocked, delayed action curative; and a second polymeric systemcomprising an acrylate resin and an initiator.
 15. The golf ball ofclaim 14, wherein the first polymeric system is saturated.
 16. The golfball of claim 14, wherein the first polymeric system further comprises acatalyst comprising an organometallic compound, tertiary amine, orcombination thereof.
 17. The golf ball of claim 14, wherein the blockeddelayed action curative comprises methylene dianiline and sodiumchloride.
 18. The golf ball of claim 14, wherein substantially all ofthe terminal isocyanate groups are blocked.
 19. The golf ball of claim14, wherein the initiator comprises benzoyl peroxide, t-amyl peroxide,or mixtures thereof.
 20. The golf ball of claim 14, further comprisingan intermediate layer.
 21. The golf ball of claim 20, wherein theportion comprises the cover.
 22. A golf ball comprising a core and acover, wherein a portion of the golf ball is formed from aninterpenetrating polymer network comprising: a first polymeric systemcomprising an isocyanate having terminal isocyanate groups, a polyol,and a blocked, delayed action curative; and a second polymeric systemcomprising an epoxy resin and a curing agent.
 23. The golf ball of claim22, wherein the curing agent is selected from the group consisting ofanhydrides, Lewis bases, amines, amides, Lewis acids, and mixturesthereof.
 24. The golf ball of claim 22, wherein the golf ball furthercomprises an intermediate layer formed of a thermoplastic material. 25.The golf ball of claim 22, wherein the blocked delayed action aminecurative comprises methylene dianiline and sodium chloride.
 26. The golfball of claim 25, wherein the blocked delayed action amine curative hasa deblocking temperature of about 175° F. to about 350° F.
 27. The golfball of claim 22, wherein at least about 95 percent or more of theterminal isocyanate groups are blocked.
 28. The golf ball of claim 22,wherein at least about 97 percent or more of the terminal isocyanategroups are blocked.